Question

If sinB = 1/2, prove that : 3 cos B – 4cos3 B = 0

Answer 1

Step-by-step explanation:

I think your question is wrong

Answer 2

sin B = 1/2

altitude = 1       hypotenuse = 2     base=?

base = √2²-1²

        = √3

cos B = √3/2

3cos B - 4cos³ B

⇒ 3× √3/2 - 4×(√3/2)³

⇒ 3√3/2  - 4× 3√3/8

⇒12√3/8 - 12√3/8  (BY TAKING L.C.M.)

⇒0

HENCE PROVED.

HOPE IT HELPS :)