Question

How do you find the exact values of cos^2(pi/3) using the half angle formula?

Answer 1

Find `cos^2 (pi/3)`

Ans: `1/4`

Explanation:

Use the trig identity: `cos 2a = 2cos^2 a - 1.`

`cos ((2pi)/3) = -1/2 = 2cos^2 (pi/3) - 1`

`2cos^2 (pi/3) = 1 - 1/2 = 1/2`

`cos^2 (pi/3) = 1/4`