Question

verify cos 3a=4cos^3 a-3 cos a, when a=30​

Answer 1

Step-by-step explanation:

when , a=30

Cos(3*30) = 4Cos³30 - 3Cos30

Cos90 = 4(√3/2)³ - 3*√3/2

0 = 4*3√3/8 - 3√3/2

0 = 3√3/2 - 3√3/2 = 0