The matrix M is given by M = ( (1, 2), (0, 1) ) ( (cosθ, -sinθ), (sinθ, cosθ) ) where 0 < θ < 2π.
- (a)The matrix M represents a sequence of two geometrical transformations in the x-y plane. State the type of each transformation, and make clear the order in which they are applied.[2]
- (b)Find the value of θ for which the transformation represented by M has a line of invariant points.[7]
Mark scheme
Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.
- [B2] Award B1 if given in the wrong order. [anticlockwise, centred at the origin, through an angle θ)], [x-axis fixed, with (0,1) mapped to (2,1).]
- [B1] M = ( (cosθ+2sinθ, -sinθ+2cosθ), (sinθ, cosθ) )
- [B1] Transforms (x,y) to (X,Y) = (x,y)
- [M1*] Uses X=x and Y=y.
- [A1] Combines equations correctly to eliminate y or x.
- [DM1 A1] Simplifies.
- [A1] θ = π/2
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