# equality trigonometry

• Feb 23rd 2011, 12:38 PM
arm
equality trigonometry
Let a, b ≠kπ : $a.sin\alpha a\sin\alpha +b. cos\alpha b\cos\alpha = a.sin\beta a\sin\beta +b. cos\beta b\cos\beta =c$.

Prove: cos^{2}\frac{\alpha- \cos^{2}\frac{\alpha- \beta }{2}=\frac{c^{2}}{a^{2}+b^{2}}.
• Feb 24th 2011, 08:47 AM
Sudharaka
Quote:

Originally Posted by arm
Let a, b ≠kπ : $a.sin\alpha a\sin\alpha +b. cos\alpha b\cos\alpha = a.sin\beta a\sin\beta +b. cos\beta b\cos\beta =c$.

Prove: $cos^{2}\frac{\alpha- \cos^{2}\frac{\alpha- \beta }{2}=\frac{c^{2}}{a^{2}+b^{2}}$

Hi arm,

When you type Latex commands always use the [ math][ /math] to wrap them.
• Feb 26th 2011, 01:08 PM
mr fantastic
Quote:

Originally Posted by arm
Let a, b ≠kπ : $a.sin\alpha a\sin\alpha +b. cos\alpha b\cos\alpha = a.sin\beta a\sin\beta +b. cos\beta b\cos\beta =c$.

Prove: cos^{2}\frac{\alpha- \cos^{2}\frac{\alpha- \beta }{2}=\frac{c^{2}}{a^{2}+b^{2}}.

The formatting of what you're trying to prove is unreadable (I am not going to bother editing it to what it should be - you can re-post it in this thread).

To get help you need to show some effort. Show your work and say where you're stuck.