Prove that:
sin 3θ=3sin θ–4sin3 θ
⇒4 sin3θ=3sinθ–sin 3θ
Now,
Substituting equation (i) in above LHS, we get
We know,
(as sin θ =sin (180°–θ))
Similarly,
(as –sin θ =sin (180°+θ))
Substituting the equation (iii) and (iv) in equation (ii), we get
We know,
Substituting this in the above equation, we get
Hence proved