Question

Rewrite with only sin x and cos x.

sin 3x

Answer 1

sin3x can be written as

sin 3x = sin(2x+x)

Now use the identity for
sin(A+B) = sinA.cosB + sinB.cosA

sin(2x+x) = sin2x.cosx + cos2x.sinx
= 2sinx.cosx.cosx + (cos^2 x - sin^2 x)sinx

Now simplify the above using identities!! :D

Understood? :)

Answer 2

2 sin x cos^2x + cos x

2 sin x cos^2x + sin^3x

sin x cos^2x - sin^3x + cos^3x

2 cos^2x sin x + sin x - 2 sin^3x

Answer 3

those are my options