# Thread: half angle conversion formulas

1. ## half angle conversion formulas

sinA+sinB+sinC=4cos1/2Acos1/2Bcos1/2C

..guys can you help me in proving this one..tnx..

2. ## Re: half angle conversion formulas

Yikes this is hard to read, some brackets or spaces would be nice ><

Is it \displaystyle \begin{align*} \sin{(A)} + \sin{(B)} + \sin{(C)} = 4\cos{\left( \frac{A}{2} \right)} \cos{\left( \frac{B}{2}\right)}\cos{\left( \frac{C}{2}\right)} \end{align*}?

3. ## Re: half angle conversion formulas

Originally Posted by fireboy25
sinA+sinB+sinC=4cos1/2Acos1/2Bcos1/2C

..guys can you help me in proving this one..tnx..
What have you been able to do with this so far?

-Dan

4. ## Re: half angle conversion formulas

Also must write the condition for this question we should have A + B + C = 180 degree.
Then use the sum and product formula: sin P + sin Q = 2 sin ( P+Q)/2 cos ( P-Q)/2 etc.

5. ## Re: half angle conversion formulas

Originally Posted by ibdutt
Also must write the condition for this question we should have A + B + C = 180 degree.
That's only if A, B, C are angles in a triangle. But it's a good question.

@fireboy25: Are A, B, and C the angles of a triangle?

-Dan

7. ## Re: half angle conversion formulas

yes..the sum of A, B, C is 180..