Question

Evaluate the following:

`sin(1/2cos^-1  4/5)`

Answer 1

`sin(1/2cos^-1  4/5)=sin{1/2xx2sin^-1+-sqrt((1-4/5)/2)}`       `[becausecos^-1x=2sin^-1+-sqrt((1-x)/2)]`

`=sin(sin^-1+-1/sqrt10)`

`=+-1/sqrt10`