Question

How on earth do I find the exact value of cos (2pi/3 - pi/6)

Do I do this?
2 pi/3 = 4/pi 6
4pi/6 - pi/6 = 3pi/6

Cos pi/6 = the square root of 3/2
So is it 3* the square root of 3 divided by two?

Answer 1

use the sum of angles formulas

Answer 2

\[\cos(A - B) = cosAcosB +sinAsinB\]