Question

How do you find the exact value using the sum or difference identities of cos pi/12?

Answer 1

`(sqrt2/4)(1 + sqrt3)`

Explanation:

Apply the trig identity:
cos ( a - b) = cos a.cos b + sin a.sin b
`cos (pi/12) = cos (pi/3 - pi/4)`
Trig table of special arcs -->
`cos (pi/12) = (1/2)(sqrt2/2) + (sqrt3/2)(sqrt2/2) =`
`= (sqrt2/4)(1 + sqrt3)`