Question

If A equal to 30°
Cos 3 A equal to 4 Cos³A - 3 Cos A​

Answer 1

I don't know the answer

Answer 2

Answer:

cos 3 a = 4 cos^3 a - 3 cos a

cos 3*30 = 4 cos (30)^3 - 3 cos 30

cos 90 = 4 cos (√3/2)^3 - 3*√3 / 2

0 = 4 * 3√3 / 8 - 3√3 2

0 = 3√3 / 2 - 3√3/2

0=0

proved