Question

If sin theta = 1/2 show that 3cos theta -4 cos ^3 theta =0

Answer 1

Answer:

sin B = 1/2

sin B = sin 30

Therefore ,

B = 30 -----( 1 )

according to the problem given,

LHS = 3(cos B ) - 4 Cos³ B

= - ( 4cos³ B - 3 cos B )

[ since cos 3x = 4cos³ x - 3 cos x ]

= - cos 3B

= - cos ( 3 × 30) from ( 1 )

= - cos 90

= 0

= RHS

Hope it helps!!