# Help solving a trig equation.

1. Mar 17, 2009

### lylos

1. The problem statement, all variables and given/known data
Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta])

2. Relevant equations
Trig identities?

3. The attempt at a solution
Tan[60 degrees]=Sin[theta]/(1/3+Cos[theta])
(1/3+Cos[theta])Tan[60 degrees]=Sin[theta]
1/3 Tan[60 degrees]=Sin[theta]-Tan[60 degrees]*Sin[theta]

Now I'm lost...
I can put it in mathematica, and get a solution of 1.34004 Radians or 76.7786 degrees. I just don't know how to solve it!

2. Mar 17, 2009

### Tom Mattson

Staff Emeritus
OK so far.

The line is wrong. Your cosine morphed into a sine, so you'll need to fix that. I would actually back up to the previous line, leaving the cosine and sine on different sides. Look at $\sin(\theta)$ on the right side. Use a Pythagorean identity to express it in terms of $\cos(\theta)$.

3. Mar 19, 2009

### lylos

Thank you, I was able to get to the solution!