Question

How do you evaluate `cos(arccos(-1))`?

Answer 1

`-1`

Explanation:

cosine and arc cosine are each inverse of the other function.

Verbally,`'cos arc cos (-1)'` is 'cosine of the angle whose cosine is `-1`'.

If `y = f(x), x = f^(-1)y, f(f^(-1)(y))=y and f^(-1)(f(x)) = x`

Here, `cos(cos^(-1)(-1))=-1`.. Also, `cos^(-1) cos pi=pi`.