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Geometric Transformations

Practice exam-style IB Math AI questions for Geometric Transformations, aligned with the syllabus and grouped by topic.

Verified by Karim
Verified by Karim
Paper
Difficulty
Status
Level
Question 1
HL • Paper 1
Easy
Calculator Permitted
HL • Paper 1
Easy
Calculator Permitted

A transformation TT is defined by

T(xy)=(2131)(xy)+(42)T\begin{pmatrix}x\\y\end{pmatrix}=\begin{pmatrix}2&-1\\3&1\end{pmatrix}\begin{pmatrix}x\\y\end{pmatrix}+\begin{pmatrix}4\\-2\end{pmatrix}
A

Find the image of the point P(3,2)P(3,-2) under TT.

[2]
B

The point QQ is mapped to Q(9,7)Q'(9,7) under TT. Find the coordinates of QQ.

[3]
Question 2
HL • Paper 1
Easy
Calculator Permitted
HL • Paper 1
Easy
Calculator Permitted

A transformation has matrix

M=(0220)\boldsymbol{M}=\begin{pmatrix}0&-2\\2&0\end{pmatrix}
A

Describe the transformation as a composition of an enlargement and a rotation about the origin.

[2]
B

A circle has radius 33 and area 9π9\pi. Find the radius and area of its image under M\boldsymbol{M}.

[3]
Question 3
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A point is rotated anticlockwise through π2\frac{\pi}{2} radians about the centre C(2,1)C(2,-1).

A

Find the affine rule for this rotation in the form X=AX+t\boldsymbol{X}'=\boldsymbol{A}\boldsymbol{X}+\boldsymbol{t}.

[3]
B

Find the image of P(5,1)P(5,1).

[2]
Question 4
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

The transformation TT is a reflection in the horizontal line y=2y=2.

A

Determine TT in the form X=AX+t\boldsymbol{X}'=\boldsymbol{A}\boldsymbol{X}+\boldsymbol{t}.

[3]
B

Find the equation of the image of the line y=x+1y=x+1 under TT.

[2]
Question 5
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

Two affine transformations are defined by

F(X)=(1101)X+(21),G(X)=(0110)X+(30)F(\boldsymbol{X})=\begin{pmatrix}1&1\\0&1\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}2\\-1\end{pmatrix}, \qquad G(\boldsymbol{X})=\begin{pmatrix}0&-1\\1&0\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}3\\0\end{pmatrix}

The transformation FF is applied first, followed by GG.

A

Find a single affine rule for the composition GFG\circ F.

[4]
B

Find the final image of the point (1,2)(1,2).

[2]
Question 6
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

Let HH be a horizontal stretch with scale factor 22, and let RR be a reflection in the line y=xy=x.

A

Find the matrix representing HH followed by RR, and hence find the image of (1,3)(1,3).

[2]
B

Find the matrix representing RR followed by HH, and hence find the image of (1,3)(1,3).

[2]
C

State what your answers demonstrate about the composition of matrix transformations.

[1]
Question 7
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A triangle has vertices A(1,1)A(1,1), B(5,1)B(5,1) and C(2,4)C(2,4). It is transformed by

T(X)=(1211)X+(23)T(\boldsymbol{X})=\begin{pmatrix}1&2\\-1&1\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}-2\\3\end{pmatrix}
A

Find the coordinates of the image vertices AA', BB' and CC'.

[3]
B

Find the area of triangle ABCA'B'C'.

[3]
Question 8
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

An iterative algorithm generates a triangular fractal with vertices A(0,0)A(0,0), B(8,0)B(8,0) and C(4,6)C(4,6). At each iteration, the current point is moved halfway towards one of the three vertices.

A triangular fractal construction showing a point $P$ moving halfway towards each of the labelled vertices $A$, $B$ and $C$. Show dashed segments from $P$ to all three vertices, with exactly one halfway point on each segment, labelled $P_A$, $P_B$ and $P_C$ respectively. In particular, remove the two open circles labelled $P_C$ on the sides of the triangle and show a single point labelled $P_C$ at the midpoint of the dashed segment $PC$, satisfying $P_C=\frac12P+\frac12C$. Retain the corresponding halfway points on $PA$ and $PB$. Do not display the transformation rules or matrix equations.
A

Write down the three affine transformations that move a point halfway towards AA, BB and CC, respectively.

[3]
B

The probabilities of selecting TAT_A, TBT_B and TCT_C are 0.200.20, 0.350.35 and 0.450.45, respectively. Find the expected number of times each transformation is selected during 50005000 iterations.

[1]
Question 9
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A graphics program enlarges a point about the origin with scale factor 12\frac12, then rotates it anticlockwise through π3\frac{\pi}{3} radians, and finally translates it by (61)\begin{pmatrix}6\\-1\end{pmatrix}.

A

Find a single affine rule for the combined transformation.

[3]
B

Find the exact image of the point (4,0)(4,0).

[2]
Question 10
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

An affine transformation has the form T(X)=AX+tT(\boldsymbol{X})=\boldsymbol{A}\boldsymbol{X}+\boldsymbol{t}. It maps

(0,0)(2,1),(1,0)(5,1),(0,1)(1,3)(0,0)\mapsto(2,-1),\qquad (1,0)\mapsto(5,1),\qquad (0,1)\mapsto(1,3)
A

Determine the matrix A\boldsymbol{A} and the translation column t\boldsymbol{t}.

[4]
B

Find the image of (2,3)(2,-3) under TT.

[2]
Question 11
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A region of area 1212 square units is transformed by

A=(k231)\boldsymbol{A}=\begin{pmatrix}k&2\\3&1\end{pmatrix}

Its image has area 3030 square units and its orientation is reversed.

A

Find the value of kk.

[3]
B

The image is then enlarged about the origin with scale factor 1.21.2. Find the area of the final image.

[2]
Question 12
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A transformation is defined by

(XY)=(2142)(xy)+(31)\begin{pmatrix}X\\Y\end{pmatrix}=\begin{pmatrix}2&-1\\-4&2\end{pmatrix}\begin{pmatrix}x\\y\end{pmatrix}+\begin{pmatrix}3\\1\end{pmatrix}
A

Show that every image point lies on the line Y=2X+7Y=-2X+7.

[3]
B

Explain why this transformation has no inverse and maps every two-dimensional region to an image of area zero.

[2]
Question 13
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A point is generated iteratively by

Xn+1=0.6Xn+(42),X0=(05)\boldsymbol{X}_{n+1}=0.6\boldsymbol{X}_n+\begin{pmatrix}4\\-2\end{pmatrix}, \qquad \boldsymbol{X}_0=\begin{pmatrix}0\\5\end{pmatrix}
A

Find X3\boldsymbol{X}_3.

[2]
B

Determine the limiting position of Xn\boldsymbol{X}_n as nn\to\infty, and justify that a limit exists.

[3]
Question 14
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

An affine transformation is defined by

T(X)=(2111)X+(34)T(\boldsymbol{X})=\begin{pmatrix}2&1\\1&1\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}-3\\4\end{pmatrix}
A

Find the inverse transformation T1T^{-1} in affine form.

[3]
B

A point is mapped to (5,2)(5,2) by TT. Find the original point.

[2]
Question 15
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A transformation is defined by

T(X)=(0.5000.25)X+(32)T(\boldsymbol{X})=\begin{pmatrix}0.5&0\\0&0.25\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}3\\-2\end{pmatrix}
A

Determine the fixed point of TT.

[2]
B

A region with area 640640 square units is transformed four times by TT. Find the area after the fourth transformation.

[3]
Question 16
HL • Paper 1
Medium
Calculator Permitted
HL • Paper 1
Medium
Calculator Permitted

A design is transformed by first reflecting it in the line y=xy=x, then applying a horizontal stretch with scale factor 33, and finally translating it by (25)\begin{pmatrix}-2\\5\end{pmatrix}.

A

Determine a single affine rule for the combined transformation.

[3]
B

State the area scale factor and whether the transformation preserves or reverses orientation.

[2]
C

The image of a point is (7,9)(7,9). Find the coordinates of the original point.

[2]
Question 17
HL • Paper 2
Medium
Calculator Permitted
HL • Paper 2
Medium
Calculator Permitted

A mapping program transforms the vertices O(0,0)O(0,0), A(4,0)A(4,0) and B(0,3)B(0,3) of a triangular region to O(2,1)O'(2,-1), A(8,1)A'(8,1) and B(1,5)B'(-1,5) respectively. The transformation has the form T(X)=MX+tT(\boldsymbol{X})=\boldsymbol{M}\boldsymbol{X}+\boldsymbol{t}.

Coordinate plane showing original triangle OAB and its image O'A'B'.
A
I.

Write down the translation column t\boldsymbol{t}.

[1]
II.

Determine the matrix M\boldsymbol{M}.

[3]
B
I.

Find the area of triangle OABO'A'B'.

[2]
II.

State whether orientation is preserved or reversed, giving a reason.

[2]
Question 18
HL • Paper 2
Medium
Calculator Permitted
HL • Paper 2
Medium
Calculator Permitted

A robot rotates every point anticlockwise through π2\frac{\pi}{2} radians about an unknown centre CC. The point P(5,2)P(5,2) is mapped to P(2,5)P'(2,5).

A
I.

Write down the matrix R\boldsymbol{R} for the rotation.

[1]
II.

Find the translation column t\boldsymbol{t} when the rotation is written as T(X)=RX+tT(\boldsymbol{X})=\boldsymbol{R}\boldsymbol{X}+\boldsymbol{t}.

[2]
B

Determine the coordinates of CC.

[3]
C

A region of area 3535 square units is transformed by TT. Find its image area and justify your answer using the determinant.

[2]
Question 19
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A logo is first stretched horizontally by scale factor 1.51.5 and then reflected in the line through the origin making an angle of 3030^\circ with the positive xx-axis.

A
I.

Write down the matrices H\boldsymbol{H} and F\boldsymbol{F} for the stretch and reflection respectively.

[2]
II.

Find the single matrix M\boldsymbol{M} representing the complete transformation.

[2]
B
I.

Find the image of the point (2,1)(2,-1).

[2]
II.

A part of the logo has area 48 cm248\text{ cm}^2. Find its image area and state whether its orientation is preserved or reversed.

[2]
Question 20
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

An affine transformation is defined by T(X)=(20.511.5)X+(32)T(\boldsymbol{X})=\begin{pmatrix}2&0.5\\-1&1.5\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}-3\\2\end{pmatrix} A triangle is mapped to a triangle with vertices (0.5,2.5)(-0.5,2.5), (7.5,1.5)(7.5,-1.5) and (1,7)(1,7).

A
I.

Find the inverse of the matrix part of TT.

[2]
II.

Hence write down an affine rule for T1T^{-1}.

[2]
B
I.

Find the three vertices of the original triangle.

[2]
II.

Verify, using areas, that the determinant gives the correct area scale factor.

[2]
Question 21
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

The position of a point is generated by the recurrence Xn+1=(00.60.60)Xn+(41),X0=(00)\boldsymbol{X}_{n+1}=\begin{pmatrix}0&-0.6\\0.6&0\end{pmatrix}\boldsymbol{X}_n+\begin{pmatrix}4\\1\end{pmatrix},\qquad \boldsymbol{X}_0=\begin{pmatrix}0\\0\end{pmatrix}

A
I.

Find X1\boldsymbol{X}_1.

[1]
II.

Find X2\boldsymbol{X}_2.

[2]
B

Determine the limiting position of Xn\boldsymbol{X}_n and justify that the sequence converges.

[3]
C

A region initially has area 200200 square units. Find its area after five applications of the transformation.

[2]
Question 22
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

An iterative design uses the vertices A(0,0)A(0,0), B(9,0)B(9,0), C(9,9)C(9,9) and D(0,9)D(0,9). At each step, the current point is moved one third of the way from a selected vertex towards its current position. Equivalently, for a selected vertex V\boldsymbol{V}, TV(X)=13X+23VT_V(\boldsymbol{X})=\frac13\boldsymbol{X}+\frac23\boldsymbol{V}

A
I.

Write down TCT_C in affine matrix form.

[1]
II.

Starting from X0=(3,6)\boldsymbol{X}_0=(3,6), find the point obtained by selecting BB and then CC.

[2]
B

A small region of area 8181 square units undergoes six iterations, with any of the four transformations selected at each step. Find its area after the sixth iteration.

[2]
C

The probabilities of selecting AA, BB, CC and DD are 0.150.15, 0.250.25, 0.400.40 and 0.200.20 respectively. Determine the expected numbers of selections of BB and CC in 1200012\,000 iterations, and explain how changing these probabilities affects the design.

[3]
Question 23
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A region of area 2424 square units is transformed by A=(k31k)\boldsymbol{A}=\begin{pmatrix}k&3\\1&k\end{pmatrix} Its image has area 6060 square units and its orientation is reversed.

A

Part (a)

I.

Show that k2=0.5k^2=0.5.

[2]
II.

The image of (1,0)(1,0) has a positive xx-coordinate. Determine kk.

[2]
B

Part (b)

I.

The image is then rotated and enlarged by a scale factor of 0.80.8. Find the area of the final image.

[2]
II.

State whether the final image has the same orientation as the original region. Justify your answer.

[2]
Question 24
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A circular region has centre (1,2)(1,-2) and radius 33. It is transformed by T(X)=(1.2000.5)X+(41)T(\boldsymbol{X})=\begin{pmatrix}1.2&0\\0&0.5\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}4\\1\end{pmatrix}

Original circle and transformed image ellipse.
A
I.

Find the centre of the image.

[2]
II.

Find the lengths of the horizontal and vertical semiaxes of the image.

[2]
B

Determine an equation of the boundary of the image ellipse.

[2]
C

Find the area of the image, giving your answer in exact form.

[2]
Question 25
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

The transformation TT is a reflection in the line y=x+2y=x+2.

Coordinate-plane diagram of the mirror line y=x+2 with a generic point and its reflected image.
A
I.

Describe a sequence of translations and a reflection in y=xy=x that produces TT.

[2]
II.

Hence determine TT in the form T(X)=AX+tT(\boldsymbol{X})=\boldsymbol{A}\boldsymbol{X}+\boldsymbol{t}.

[2]
B

Find the equation of the image of the line 2xy=12x-y=1 under TT.

[3]
C

State the area scale factor and the effect on orientation.

[1]
Question 26
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A theatre projects a rectangular image with vertices O(0,0)O(0,0), P(5,0)P(5,0), Q(5,3)Q(5,3) and R(0,3)R(0,3). The projector applies the affine transformation

T(X)=(1.20.40.30.9)X+(62)T(\boldsymbol X)=\begin{pmatrix}1.2&0.4\\-0.3&0.9\end{pmatrix}\boldsymbol X+\begin{pmatrix}6\\2\end{pmatrix}
Original theatre image rectangle with labelled vertices.
A
I.

Find the coordinates of QQ', the image of QQ.

[2]
II.

Find the area of the projected image.

[2]
B

A mark on the projected image has coordinates (10.8,3.5)(10.8,3.5). Determine its coordinates in the original rectangle.

[3]
C

The projector is recalibrated by replacing 0.40.4 in the matrix by a parameter kk. Determine all values of kk for which the projected rectangle has area 1515 square units, and state which value reverses its orientation.

[4]
Question 27
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A light on a rotating fairground ride is initially at X0=(8,1)X_0=(8,1). During each step, the vector from CC to the light is multiplied by 0.90.9 and rotated anticlockwise through π6\frac{\pi}{6}, where C=(2,1)C=(2,1).

Centre and early points of the light's spiral path.
A
I.

Write the transformation in the form Xn+1=AXn+tX_{n+1}=AX_n+t.

[2]
II.

Find X3X_3.

[2]
B

Determine the first value of nn for which the light is less than 11 unit from CC.

[3]
C

A small triangular plate attached to the light undergoes the same affine transformation as the light at each step and has initial area 2424 square units. Determine its area after nn steps and hence find the first step at which its area is less than 11 square unit. Explain why the rotation does not affect this result.

[4]
Question 28
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A textile motif is processed using a horizontal stretch
H=(1.5001)H=\begin{pmatrix}1.5&0\\0&1\end{pmatrix}
and a reflection FF in the line y=xy=x. The motif contains the point P=(2,4)P=(2,4).

Triangle motif with point P and its two transformed images.
A
I.

Find the matrix and image of PP when HH is applied first, followed by FF.

[2]
II.

Find the matrix and image of PP when FF is applied first, followed by HH.

[2]
B

The original motif has area 1818 square units. Compare the areas and orientations of the two images.

[3]
C

Replace 1.51.5 by a non-zero horizontal scale factor kk. Determine the values of kk for which FH=HFFH=HF, and interpret the result geometrically.

[3]
Question 29
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A camera sensor applies a horizontal stretch with scale factor 1.251.25, a vertical compression with scale factor 0.80.8, and then an anticlockwise rotation through angle θ\theta. A rectangular sensor region has vertices (0,0)(0,0), (6,0)(6,0), (6,4)(6,4) and (0,4)(0,4).

Rectangle and transformed image at θ=π/6.
A
I.

Write down the combined transformation matrix MθM_\theta.

[2]
II.

Find detMθ\det M_\theta and interpret its value.

[2]
B

For θ=π6\theta=\frac{\pi}{6}, determine the coordinates of the image of (2,1)(2,1).

[3]
C

A technician reverses the order, rotating first and then applying the two stretches. Determine all values of θ\theta in 0θ<2π0\leq\theta<2\pi for which the two orders produce the same transformation.

[3]
Question 30
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A digital image occupies the rectangular region 0x8000\leq x\leq800, 0y6000\leq y\leq600, where coordinates are measured in pixels. It is transformed by
T(X)=(0.80.30.20.9)X+(12050)T(X)=\begin{pmatrix}0.8&-0.3\\0.2&0.9\end{pmatrix}X+\begin{pmatrix}120\\50\end{pmatrix}

Original rectangle, transformed image, and bounding box.
A
I.

Find the images of (800,0)(800,0) and (0,600)(0,600).

[2]
II.

Find the image of (800,600)(800,600).

[2]
B

Determine the dimensions and area of the smallest axis-aligned rectangle containing the transformed image.

[3]
C

Find the actual area of the transformed image and determine the percentage of the bounding rectangle that is not occupied by the image.

[3]
Question 31
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A transformation is defined by T(xy)=(2412)(xy)+(35)T\begin{pmatrix}x\\y\end{pmatrix}=\begin{pmatrix}2&-4\\-1&2\end{pmatrix}\begin{pmatrix}x\\y\end{pmatrix}+\begin{pmatrix}3\\5\end{pmatrix}

A
I.

Show that every image point (X,Y)(X,Y) lies on the line Y=12X+132Y=-\frac12X+\frac{13}{2}.

[2]
II.

Explain why TT has no inverse.

[2]
B

The unit square has vertices (0,0)(0,0), (1,0)(1,0), (1,1)(1,1) and (0,1)(0,1). Determine the endpoints of its image and find the length of the resulting line segment.

[4]
Question 32
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

Let H\boldsymbol{H} represent a horizontal stretch of scale factor 22, and let R\boldsymbol{R} represent an anticlockwise rotation through 4545^\circ about the origin.

A
I.

Find the matrix RH\boldsymbol{R}\boldsymbol{H} representing the stretch followed by the rotation.

[2]
II.

Find the matrix HR\boldsymbol{H}\boldsymbol{R} representing the rotation followed by the stretch.

[2]
B
I.

Determine all points whose images are the same under the two compositions.

[3]
II.

Compare the area scale factors of the two compositions.

[1]
Question 33
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

To align two medical images, a similarity transformation maps A(1,2)A(1,2) to A(6,1)A'(6,-1) and B(5,2)B(5,2) to B(6,7)B'(6,7). The transformation consists of an enlargement, a rotation and a translation.

A
I.

Determine the enlargement scale factor and the angle and direction of rotation.

[2]
II.

Find a single affine rule for the alignment.

[2]
B

The same transformation can be described as an enlargement and rotation about a common fixed centre, with no separate translation. Determine this centre.

[3]
C

State the area scale factor of the alignment.

[1]
Question 34
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A point is generated iteratively by Xn+1=0.5Xn+(63),X0=(24)\boldsymbol{X}_{n+1}=-0.5\boldsymbol{X}_n+\begin{pmatrix}6\\-3\end{pmatrix},\qquad \boldsymbol{X}_0=\begin{pmatrix}2\\4\end{pmatrix}

A
I.

Describe geometrically the matrix transformation X0.5X\boldsymbol{X}\mapsto-0.5\boldsymbol{X}.

[1]
II.

Determine the fixed point C\boldsymbol{C} of the affine transformation.

[2]
B

Show that Xn=C+(0.5)n(X0C)\boldsymbol{X}_n=\boldsymbol{C}+(-0.5)^n(\boldsymbol{X}_0-\boldsymbol{C}) and hence find X3\boldsymbol{X}_3.

[3]
C

Find the least value of nn for which the distance from Xn\boldsymbol{X}_n to C\boldsymbol{C} is less than 0.010.01.

[2]
Question 35
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A digital image is rotated clockwise through 3030^\circ, then stretched horizontally by scale factor 1.41.4 and vertically by scale factor 0.80.8, and finally translated by (12080)\begin{pmatrix}120\\80\end{pmatrix} pixels.

A
I.

Find the matrix M\boldsymbol{M} representing the rotation followed by the stretches.

[2]
II.

Find the final image of the pixel at (100,50)(100,50), giving coordinates to three significant figures.

[2]
B

The pixel (20,10)(20,-10) is mapped to approximately (137.248,65.072)(137.248,65.072). Describe how an inverse calculation recovers the original pixel and verify its coordinates.

[2]
C

An original image region contains 250000250\,000 square pixels. Estimate the area of its transformed image.

[2]
Question 36
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

To align two aerial photographs, three landmarks have coordinates A(1,2)A(1,2), B(5,2)B(5,2) and C(2,6)C(2,6) in the first photograph. Their corresponding coordinates in the second photograph are A(4,1)A'(4,1), B(10,3)B'(10,3) and C(3,10)C'(3,10). An affine transformation T(X)=MX+tT(X)=MX+t is used.

Landmark

First photo x

First photo y

Second photo x

Second photo y

A

1

2

4

1

B

5

2

10

3

C

2

6

3

10

D'

12

8

A
I.

Use the images of AA and BB to determine the first column of MM.

[2]
II.

Hence determine MM and tt.

[2]
B

A lake has area 2.40 km22.40\ \text{km}^2 in the first photograph. Find its represented area in the second photograph and state whether its orientation is preserved.

[3]
C

A fourth landmark is recorded as D=(12,8)D'=(12,8) in the second photograph. Determine its coordinates in the first photograph. Explain why a unique answer exists.

[4]
Question 37
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A fractal is generated inside the unit square. At each stage, every square is replaced by four copies, each with linear scale factor 0.40.4, positioned at the four corners. The lower-left corner transformations include
T0(X)=0.4X,T1(X)=0.4X+(0.60)T_0(X)=0.4X,\qquad T_1(X)=0.4X+\begin{pmatrix}0.6\\0\end{pmatrix}
The other two transformations are denoted by T2T_2 and T3T_3.

The first three stages of a corner-square fractal, showing four contracted copies at each stage and a central cross-shaped gap.
A
I.

Write down T2T_2 and T3T_3 for the upper-left and upper-right copies respectively.

[2]
II.

Find the image of (0,0)(0,0) after applying T1T_1, then T2T_2, then T3T_3.

[2]
B
I.

Find the total area of all squares at stage nn, where the original square is stage 00.

[2]
II.

Determine the first stage for which the total area is less than 0.010.01 square units.

[2]
C

A point is generated by repeatedly applying T3T_3, starting at the origin. Determine its limiting position and justify that the limit exists.

[4]
Question 38
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A logo is transformed by the parameter-dependent matrix
Ak=(k21k1)A_k=\begin{pmatrix}k&2\\1&k-1\end{pmatrix}
followed by a translation through (4,3)(4,-3). The original logo has area 2020 square units.

Three transformed versions of the same logo: one ordinary polygon and two collapsed line images.
A
I.

Find the determinant of AkA_k.

[1]
II.

Determine the values of kk for which the logo collapses onto a line.

[3]
B

For k=2k=2, show that every image point lies on a straight line and find the equation of this line.

[3]
C

Determine the intervals of kk for which the image has area greater than 2020 square units and preserves orientation.

[3]
Question 39
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A robotic camera repeatedly corrects the position of a target using

Xn+1=(0.60.200.5)Xn+(41),X0=(06)X_{n+1}=\begin{pmatrix}0.6&0.2\\0&0.5\end{pmatrix}X_n+\begin{pmatrix}4\\-1\end{pmatrix}, \qquad X_0=\begin{pmatrix}0\\6\end{pmatrix}
Corrected target positions for successive camera corrections.
A
I.

Find X1X_1 and X2X_2.

[2]
II.

Determine the fixed point LL of the correction.

[2]
B

Show that XnL=An(X0L)X_n-L=A^n(X_0-L), where AA is the matrix in the recurrence.

[3]
C

Use technology to determine the least value of nn for which both coordinates of XnX_n are within 0.010.01 of the corresponding coordinates of LL. Justify why the sequence converges.

[4]
Question 40
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A cartographer investigates the family of map transformations
Tp(X)=(p12p+1)X+(54)T_p(X)=\begin{pmatrix}p&1\\2&p+1\end{pmatrix}X+\begin{pmatrix}-5\\4\end{pmatrix}
A protected region has area 36 km236\ \text{km}^2.

Area scale factor of the affine image as p varies.
A
I.

Find the determinant of the transformation matrix.

[1]
II.

Determine the values of pp for which the map preserves area.

[3]
B

For p=2p=2, find the image area and state whether orientation is preserved.

[2]
C

Determine the interval of values of pp for which the image area is less than 18 km218\ \text{km}^2.

[4]
Question 41
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A kaleidoscope uses two mirrors through the origin. Mirror L1L_1 lies along the xx-axis and mirror L2L_2 makes an anticlockwise angle ϕ\phi with the xx-axis. Reflection in L1L_1 is applied first, followed by reflection in L2L_2.

A kaleidoscope diagram with two intersecting mirror lines, the angle between them labelled phi, and a motif with its two successive reflected images.
A
I.

Write reflection in L2L_2 as a composition involving rotations and reflection in the xx-axis.

[2]
II.

For ϕ=π5\phi=\frac{\pi}{5}, find the image of (3,0)(3,0) after both reflections.

[2]
B

Show that, for general ϕ\phi, the composition is a rotation through 2ϕ2\phi.

[3]
C

For ϕ=π5\phi=\frac{\pi}{5}, determine the least positive number of repeated pairs of reflections required to return every point to its original position. Justify your answer.

[3]
Question 42
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A medical scan is aligned with a reference image using a rotation, a positive enlargement and a translation. The transformation has the form X=sRθX+tX'=sR_\theta X+t, where s>0s>0, the rotation and enlargement are about the origin, and the translation is applied last. In the scan, landmarks are A=(1,2)A=(1,2) and B=(5,2)B=(5,2). In the reference image, they are A=(7,4)A'=(7,4) and B=(7,10)B'=(7,10).

Scan and reference landmark coordinates for the alignment transformation.
A
I.

Determine the enlargement scale factor and angle of rotation.

[2]
II.

Determine the translation column.

[2]
B

A third landmark is C=(3,6)C=(3,6). Find its predicted position in the reference image.

[3]
C

A tumour region has area 12.0 cm212.0\ \text{cm}^2 in the scan. Find its area in the reference image. The observed position of the third landmark is (1.4,6.7)(1.4,6.7). Calculate the alignment error and comment on the suitability of the model if errors below 0.50.5 coordinate units are considered acceptable.

[4]
Question 43
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A stage-lighting system uses a horizontal shear
Hh=(1h01)H_h=\begin{pmatrix}1&h\\0&1\end{pmatrix}
and a vertical shear
Vk=(10k1)V_k=\begin{pmatrix}1&0\\k&1\end{pmatrix}
A square beam has area 1616 square units. The graph illustrates the particular case h=k=1h=k=1; the following results should be obtained for general hh and kk.

Square beam and its images under opposite shear orders.
A
I.

Find the matrix when HhH_h is applied first, followed by VkV_k.

[2]
II.

Find the matrix when the order is reversed.

[2]
B

Determine the area and orientation of the beam after either composition.

[3]
C

Determine the condition on hh and kk for the two shears to commute, and interpret the condition.

[3]
Question 44
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

A snowflake boundary begins with the line segment from A(0,0)A(0,0) to B(9,0)B(9,0). At each iteration, every segment is replaced by four segments, each one third as long. The middle two segments form the sides of an outward equilateral triangle.

Initial segment and first snowflake iteration.
A
I.

Derive the exact coordinates of the three intermediate vertices after the first iteration, giving the geometric calculations used.

[2]
II.

Write affine rules for the two required similarity transformations mapping the original segment onto the second and third segments. Each rule must scale by 13\frac13, rotate through +π3+\frac{\pi}{3} for the second segment or π3-\frac{\pi}{3} for the third, and then translate.

[2]
B
I.

Show that the total boundary length after nn iterations is 9(43)n9\left(\frac43\right)^n.

[2]
II.

Find the least value of nn for which the boundary length exceeds 5050 units.

[2]
Question 45
HL • Paper 2
Hard
Calculator Permitted
HL • Paper 2
Hard
Calculator Permitted

An affine transformation is defined by T(X)=(0.60.80.80.6)X+(24)T(\boldsymbol{X})=\begin{pmatrix}0.6&0.8\\0.8&-0.6\end{pmatrix}\boldsymbol{X}+\begin{pmatrix}-2\\4\end{pmatrix}

A
I.

Show that the matrix part represents a reflection.

[2]
II.

Find the angle made by the reflection axis of the matrix part with the positive xx-axis.

[1]
B

Determine the equation of the fixed line of the full affine transformation TT.

[3]
C

Show that applying TT twice returns every point to its original position.

[2]
Question 46
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A surveying program reflects points in the line :y=12x+3\ell:y=\frac12x+3. Let α=tan1(12)\alpha=\tan^{-1}(\frac12), and let RθR_\theta denote an anticlockwise rotation through θ\theta about the origin.

Mirror line ℓ with the original point P only.
A
I.

Explain why reflection in the line y=12xy=\frac12x has matrix Rα(1001)RαR_\alpha\begin{pmatrix}1&0\\0&-1\end{pmatrix}R_{-\alpha}.

[2]
II.

Find this matrix exactly.

[2]
B

Determine an affine rule for reflection in \ell, and hence find the image of P=(7,1)P=(7,1).

[4]
C

Show that applying this affine transformation twice returns every point to its original position.

[4]
Question 47
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

A fractal path begins with a unit segment from (0,0)(0,0) to (1,0)(1,0). Each segment is replaced by four segments of scale factor 13\frac13, with successive directions 00, π3\frac{\pi}{3}, π3-\frac{\pi}{3} and 00 relative to the original segment. Let RθR_\theta denote rotation through θ\theta. Call the initial unit segment stage 0; stage nn is obtained after nn replacements.

The initial segment and the first two stages of a Koch-type path, with the four replacement segments and their relative directions indicated.
A
I.

Write the matrix used for the second replacement segment.

[2]
II.

Determine the translation required so that this second segment begins at (13,0)(\frac13,0).

[2]
B

Show that the four replacement segments have resultant displacement (1,0)(1,0).

[3]
C

Find the total length after stage nn and determine the first stage at which it exceeds 1010. Explain why the endpoints remain unchanged at every stage.

[4]
Question 48
HL • Paper 3
Hard
Calculator Permitted
HL • Paper 3
Hard
Calculator Permitted

An animated particle follows the affine recurrence

Xn+1=0.85Rπ/4Xn+(32),X0=(80)X_{n+1}=0.85R_{\pi/4}X_n+\begin{pmatrix}3\\-2\end{pmatrix}, \qquad X_0=\begin{pmatrix}8\\0\end{pmatrix}

Let A=0.85Rπ/4A=0.85R_{\pi/4}.

Particle positions in an inward polygonal spiral toward L.
A
I.

Find X1X_1.

[2]
II.

Determine the fixed point LL of the recurrence.

[2]
B

Show that
Xn=L+0.85nRnπ/4(X0L)X_n=L+0.85^nR_{n\pi/4}(X_0-L)

[4]
C

Determine the first value of nn for which XnX_n is within 0.10.1 units of LL. Hence describe the long-term motion of the particle.

[4]

Geometry of 3D Shapes