# Matrix proof question

1. Mar 14, 2013

### Michael_Light

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

I understand that matrix in the form of A as above represents a rotation about the origin.. but for this question, I am actually clueless on what method should i use to prove it... Any hint?

2. Mar 15, 2013

### Staff: Mentor

Seems like a natural for an induction proof.

3. Mar 15, 2013

### HallsofIvy

It looks to me to be almost trivial! What is $A^2$? $A^{2n}= (A^2)^n$.