Question

How do you find `cos ^ -1 (0)` without a calculator?

Answer 1

Go through the cosines of special angles until you get to one whose cosine is `0`

Explanation:

#{: (bb"Special Angle (rad)", bb"Cosine"), (" "" "" "0," "1),(" "" "" "pi/6," "sqrt3/2),(" "" "" "pi/4," "sqrt2/2),(" "" "" "pi/3," "1/2),(" "" "" "pi/2," "0):}#

`pi/2` is in the range of `cos^-1`, so we get

`cos^-1 0 = pi/2`