# Thread: not sure what to do

1. ## not sure what to do

cos^2(18) - sin^2(18)

2. ## Re: not sure what to do

Originally Posted by notme
cos^2(18) - sin^2(18)
HINT: $\cos(2\theta)=\cos^2(\theta)-\sin^2(\theta)$

3. ## Re: not sure what to do

What did this problem ask you to do? What you have is a trig expression. What do you want to do with it?

4. ## Re: not sure what to do

Originally Posted by HallsofIvy
What do you want to do with it?
How would I know?

5. ## Re: not sure what to do

Nobody was talking to you!