Q185 · Practice questionTechnology-freeComplex unfamiliar7 marks
QUESTION 185 (7 marks)
A game map has triangular zone with complex coordinates . A portal transforms coordinates by .
a)[2 marks]
Determine the three transformed vertices.
b)[2 marks]
Determine the transformed area and explain the change in area.
c)[3 marks]
Write the transformation as . Determine and , and use the determinant to check your area scale factor.
WORKED SOLUTION
7 marksPractice marking scheme
ANSWER
(a) . (b) square units; doubled. (c) , , .
Worked solution
(a) Substitution of 0 gives , of 2 gives , and of 2i gives .
(b) The points and i form a horizontal base of length 4; is two units below it, so area is . Multiplication by scales lengths by , and area by 2. Rotation and translation preserve area.
(c) For , . Thus the linear part is and the translation is . Its determinant is , so areas double, consistent with part (b). Translation leaves area unchanged.
Equivalent mathematically justified methods accepted.
Exact answers unless a decimal accuracy is specified.
Part a: Find the image of the origin.
Part a: Find both other images.
Part b: Calculate transformed area 4.
Part b: Explain squared length scaling and doubled area.
Part c: Extract both real coordinate equations.
Part c: State the matrix and translation.
Part c: Use the absolute determinant to confirm the scale factor.
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