Hello, I was wondering if someone could help me with the proof of $\displaystyle cos(arcsin(x))=sqrt(1-x^2)$. I'm a little confused, I was using cos=sqrt(1-x^2) and arcsin=1/(sqrt(1-x^2)) and getting no where. A trigonometric proof isn't needed but if it's the only way then that's fine. Thanks for all help!