ECZ 2017 · O-Level Paper 2 · Question 12 — Geometrical Transformations

Using a scale of 1 cm to represent 1 unit on each axis, draw x and y axes for -6 ≤ x ≤ 10 and -10 ≤ y ≤ 8.

(a) A quadrilateral ABCD has vertices A(-5, 7), B(-4, 8), C(-3, 7) and D(-4, 4) while its image has vertices A1(-5, -3), B1(-6, -2), C1(-5, -1) and D1(-2, -2).

(a(i)) Draw and label the quadrilateral ABCD and its image A1B1C1D1.[2]

Verified working — step 1

Plot A(-5, 7), B(-4, 8), C(-3, 7), D(-4, 4) and join in order.

(a(ii)) Describe fully the transformation which maps quadrilateral ABCD onto quadrilateral A1B1C1D1.[3]

Verified working — step 1

The mapping is (x, y) → (2 - y, x + 2), a quarter turn.

(b) The matrix -2001 maps the quadrilateral ABCD onto the quadrilateral A2B2C2D2.

(b(i)) Find the coordinates of the vertices of the quadrilateral A2B2C2D2.[2]

Verified working — step 1

The matrix -2001 sends (x, y) to (-2x, y).

(b(ii)) Draw and label the quadrilateral A2B2C2D2.[1]

Verified working — step 1

Plot A2(10, 7), B2(8, 8)…

(c) The quadrilateral ABCD is mapped onto the quadrilateral A3B3C3D3 where A3 is (4, -8), B3 is (2, -10), C3 is (0, -8) and D3 is (2, -2). Describe fully this transformation.[4]

Verified working — step 1

The mapping is (x, y) → (-2x - 6, -2y + 6), whose linear part is -2 times the identity: an enlargement, scale factor -2.

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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