Question

How do you evaluate `cos^2(pi/12)-sin^2(pi/12)`?

Answer 1

`cos^2(pi/12)-sin^2(pi/12)=sqrt3/2`

Explanation:

To evaluate `cos^2(pi/12)-sin^2(pi/12)`, recall the identity

`cos2theta=cos^2theta-sin^2theta`

Hence, `cos^2(pi/12)-sin^2(pi/12)=cos2xx(pi/12)=cos(pi/6)=sqrt3/2`