# Simplify with Trigonometric Identities

1. Sep 6, 2014

### KleZMeR

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

I'm trying to simplify some trigonometric expressions, I'm attaching my work here. This comes from a famous physics problem i.e. the rod with two masses spinning on a circle. I've tried many times but I just can't get it. Any help on which identities to use would really help me.

2. Relevant equations

I'm attaching the simplified version, the 'answer'

3. The attempt at a solution

I'm attaching my work.

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2. Sep 6, 2014

### Staff: Mentor

Apply a couple of times sin2 x + cos2 x = 1

3. Sep 6, 2014

### KleZMeR

Yes, I looked at that identity, but there are 2 different angles in this problem, and also one of my last two terms is dø2*sin2Θ

Any direction on how to first apply the identity would also help?

4. Sep 6, 2014

### Staff: Mentor

Take cos2 θ outside some brackets because it's a common factor.

And you'll see again, there's another common factor in two other terms to treat similarly.