Maybe it's me, but this didn't seem easy!?!? I'm getting an answer of sin a = 1; is this correct?
Here's a summary of what I did:
You have the cosine of a difference identity:
Use the Law of sines to write sin b in terms of sin a:
Use the pythagorean identity to write cosine in terms of sine:
Plug (2), (3a), and (3b) into (1), plus the fact that cos (a-b) = 3/4:
Solved for sin a and I got sin a = 1.
I'm sure I did something wrong here.