Question

If sin B =1/2
show that
3 cos B - 4 cos3 B=0.​

Answer 1

Answer:

sin B=1/2

therefore ,sin B=sin 30°=1/2

cos 30°=√3/2

3 cos B-4 cos³B

3×√3/2 -4×(√3/2)³

3√3/2 - 12√3/8

3√3/2 -3√3/2=0