Prove the identity. 3 tan(3x) = (9 tan(x) − 3 tan^3(x)) /1 − 3 tan^2(x)

Answer 1

Manipulate the left side of the equation 3tan(3x) by considering it as 3tan(x + 2x). Then use the angle sum identity for tangent:

Then use the double angle identity for tangent:

Get common denominators and simplify

Answer 2

Hi Madison P.,

Looks like you might need to work your way upwards from an identity for tan(x+x) ?

-- Cheers, --Mr. d.