Provide an exact evaluation of the expression cos 8 degree c

Provide an exact evaluation of the expression: cos (8 degree) cos (22 degree) - sin (8 degree) sin (22 degree). 1/2 -1/2 Squareroot 3/2 - Squareroot 3/2

Solution

cos 8 cos 22- sin 8 sin 22

This is of the form cos a cos b - sin a sin b which is equal to cos (a+b)

Therefore cos 8 cos 22- sin 8 sin 22=cos(8+22)=cos 30=sqrt3/2

Correct option is the third option