# Homework Help: Parametric equation question

1. Jun 5, 2010

### stau40

1. The problem statement, all variables and given/known data
Find the length of the path over (2 cos t - cos 2t, 2 sin t - sin 2t) 0<=t<=(pi/2)

2. Relevant equations
sin^(2) x = (1-cos 2x)/2

3. The attempt at a solution
I have worked my way thru the problem and I have arrived at 2 (sq root 2) antiderivative (sq root (1-cos t)), but I'm not sure how this coverts into the relevant equation above? Thanks in advance!

2. Jun 5, 2010

### xcvxcvvc

$$\sqrt{1 - cos(t)} = \sqrt{\frac{2(1 - cos(t))}{2}}=\sqrt{2sin^2(\frac{t}{2})}=\sqrt{2}sin(\frac{t}{2})$$