Date | May Example question | Marks available | 1 | Reference code | EXM.3.AHL.TZ0.5 |
Level | Additional Higher Level | Paper | Paper 3 | Time zone | Time zone 0 |
Command term | Show that | Question number | 5 | Adapted from | N/A |
Question
This question will diagonalize a matrix and apply this to the transformation of a curve.
Let the matrix M=(52121252).
Let (1√21√2−1√21√2)=R−1.
Let R(xy)=(XY).
Let (1√3001√2)(XY)=(uv).
Hence state the geometrical shape represented by
Find the eigenvalues for M. For each eigenvalue find the set of associated eigenvectors.
Show that the matrix equation (xy)M(xy)=(6) is equivalent to the Cartesian equation 52x2+xy+52y2=6.
Show that (1√2−1√2) and (1√21√2) are unit eigenvectors and that they correspond to different eigenvalues.
Hence, show that M(1√21√2−1√21√2)=(1√21√2−1√21√2)(2003).
Find matrix R.
Show that M=R−1(2003)R.
Verify that (XY)=(xy)R−1.
Hence, find the Cartesian equation satisfied by X and Y.
Find the Cartesian equation satisfied by u and v and state the geometric shape that this curve represents.
State geometrically what transformation the matrix R represents.
the curve in X and Y in part (e) (ii), giving a reason.
the curve in x and y in part (b).
Write down the equations of two lines of symmetry for the curve in x and y in part (b).
Markscheme
|52−λ121252−λ|=0⇒(52−λ)2−(12)2=0⇒52−λ=±12⇒λ=2or3 M1M1A1A1
λ=2 (12121212)(pq)=(00)⇒q=−p eigenvalues are of the form t(1−1) M1A1
λ=3 (−121212−12)(pq)=(00)⇒q=p eigenvalues are of the form t(11) M1A1
[8 marks]
(xy)(52121252)(xy)=(6)⇒(52x+12y12x+52y)(xy)=(6) M1A1
⇒(52x2+12xy+12xy+52y2)=(6)⇒52x2+xy+52y2=6. AG
[2 marks]
(1√2−1√2)=1√2(1−1) corresponding to λ=2, (1√21√2)=1√2(11) corresponding to λ=3 R1R1
[2 marks]
M(1√2−1√2)=2(1√2−1√2)andM(1√21√2)=3(1√21√2)⇒M(1√21√2−1√21√2)=(1√21√2−1√21√2)(2003) A1AG
[1 mark]
Determinant is 1. R=(1√2−1√21√21√2) M1A1
[2 marks]
MR−1=R−1(2003) so post multiplying by R gives M=R−1(2003)R M1AG
[1 mark]
(1√2−1√21√21√2)(xy)=(XY)⇒(1√2x−1√2y1√2x+1√2y)=(XY)⇒(XY)=(1√2x−1√2y1√2x+1√2y) M1A1
and (xy)(1√21√2−1√21√2)=(1√2x−1√2y1√2x+1√2y) completing the proof A1AG
[3 marks]
(xy)M(xy)=(6)⇒(xy)R−1(2003)R(xy)=(6)⇒(XY)(2003)(XY)=(6)
⇒(2X2+3Y2)=(6)⇒X23+Y22=1 M1A1
[2 marks]
X√3=u,Y√2=v⇒u2+v2=1, a circle (centre at the origin radius of 1) A1A1
[2 marks]
A rotation about the origin through an angle of 45° anticlockwise. A1A1
[2 marks]
an ellipse, since the matrix represents a vertical and a horizontal stretch R1A1
[2 marks]
an ellipse A1
[1 mark]
y=x, y=−x A1A1
[2 marks]