Question

How do you evaluate `cos^-1 (0)`?

Answer 1

`cos^-1 0=pi/2`.

Explanation:

We use the Defn. of `cos^-1 : cos^-1x=theta, |x|<=1 iff costheta=x, theta in [0,pi]`

Since, `cos(pi/2)=0, &, pi/2 in [0,pi], cos^-1 0=pi/2`.