Question

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

Answer 1

`( 2 k + 1 )pi, k =0, +-1, +-2, +-3...`

Explanation:

If `a = cos^(-1)(-1), cos a = -1`
If the range of a is specified as , say, `[0, 2 pi ], a = pi`.
The general solution is a = `( 2 k + 1 )pi, k =0, +-1, +-2, +-3...`