# Having some trouble

• Dec 3rd 2008, 11:18 PM
Sinsane
Having some trouble
I couldnt figure this one out...can anyone?

cos(arcsin3/5 + arccos sqrt3/2)

Thanks!
• Dec 4th 2008, 04:12 AM
mr fantastic
Quote:

Originally Posted by Sinsane
I couldnt figure this one out...can anyone?

cos(arcsin3/5 + arccos sqrt3/2)

Thanks!

Start by letting $\sin^{-1} \frac{3}{5} = \alpha \Rightarrow \sin \alpha = \frac{3}{5}$ and $\cos^{-1} \frac{\sqrt{3}}{2} = \beta \Rightarrow \cos \beta = \frac{\sqrt{3}}{2}$.

Your task is to calculate $\cos (\alpha + \beta)$. Hint: Start by applying the compound angle formula and then make the necessary substitutions.
• Dec 4th 2008, 04:49 AM
Sinsane
Thank you..I finally figured it out before you said something..but I appreciate the help. But its always good to make sure something is right haha.