Question

If 2sinA-1=0 show that:
Sin3A=3sinA-4sin^3A

Answer 1

Step-by-step explanation:

Given

2 sin A-1=0

sin A=1/2

sin A=sin 30

A=30 degrees

put A=30

LHS =sin 3A

=sin 3 (30)=sin 90 =1

RHS=3 sinA -4sin^3A

=3sin30-4 sin^3 (30)

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

=3/2-4/8=3/2-1/2=2/2=1

• LHS=RHS
• hence proved