Question

How do you find the exact value of tan2x using the double angle formula?

Answer 1

`tan2x=(2tanx)/(1-tan^2x)`

Proof:

`tan2x = (sin2x)/(cos2x)=(2sinxcosx)/(cos^2x-sin^2x)=((2sinxcosx)/(cos^2x))/(1-(sin^2x)/(cos^2x))=(2tanx)/(1-tan^2x)`

QED