Question

How do you find exact value of `cos (pi/ 2)`?

Answer 1

`cos(pi/2)=0`

Explanation:

For an angle in standard position `cos(theta)=x/r` (definition).

From the images below, we can see that as `thetararrpi/2`
`color(white)("XXX")x rarr 0`

Which implies that as `theta rarr pi/2`
`color(white)("XXX")cos(theta) rarr 0/r =0`