Question

if sin = √3/2 , show that 4 cos³-3 cos =-1​

Answer 1

Answer:

sin A = √3/2

means A = 60°

so cos 60°= 1/2

Now LHS = 4Cos^3 A - 3 Cos A

= 4(1/2)^3 - 3 (1/2)

= 4/8 - 3/2=(4-12)/8

= -8/8 = -1 = RHS