Calculating the exact value of an inverse

[trap]

cos[ sin^-1 (1/2) + sin^-1 (-1) ]

appreciate any help on this

 

[so-crates]

cos(a+b) = ?

 

[trap]

ohh, yes, thanks, how dumb i am...

 

[dextercioby]

\arcsin \ \frac{1}{2}=\frac{\pi}{6}

\arcsin \ -1=-\frac{\pi}{2}

Add the 2 results and end up with -\frac{\pi}{3}

And then
\cos \ -\frac{\pi}{3} =\frac{1}{2}

Daniel.