If tan(x)=4/9 (in Quadrant-I), Find tan(2x)=

Question

I know in order to answer this I have to find cos(2x) and sin(2x), and then divide sin(2x)/cos(2x) to get tan (2x). I'm just not sure how to go about finding them. Any help would be appreciated.

Answer 1

tan(2x) = [2tanx] / [1-tan^2x]

= 2(4/9) / [1 - 16/81]

= (8/9) / (65/81) = 72/65