# Math Help - One angle of triangle

1. ## One angle of triangle

I'm not sure what formula is needed to answer the attached question. Maybe the half angle formulae?

2. Hello Stuck Man
Originally Posted by Stuck Man
I'm not sure what formula is needed to answer the attached question. Maybe the half angle formulae?
$\sin A = \sin(\pi-A)$
$=\sin(B+C)$

$=\sin B\cos C + \cos B \sin C$
Can you see it OK from here?

Grandad

3. Grandad had answered the question by the time I written my reply. So I removed it.

4. Dontcha just hate when he does that!

5. I found the solution by solving sin C and cos C. Thanks.