Question

How do you use the half angle formula to simplify `cos^2(pi/3)`?

Answer 1

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

#2cos^2 (pi/3) = 1 + cos (2pi)/3

Trig table gives `cos ((2pi)/3) = -1/2`

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