Question

How do you use the half angle identity to find exact value of cos 75 degrees?

Answer 1

`(sqrt(2-sqrt3))/2`

Explanation:

`cos75=cos(5pi/12)=cos((5pi/6)/2)=sqrt((1+cos(5pi/6))/2)=`
`=sqrt((1-cos(pi/6))/2)=sqrt((1-sqrt3/2)/2)=sqrt((2-sqrt3)/4)=`
`=sqrt(2-sqrt3)/2`