Posted by Anonymous on .
Given that tan x= 3/4 and x is in the second quadrant. Find sin 2x, cos 2x, and tan 2x (Exact, no decimals).
Please show stepbystep, thank you!

Trig Question 
Reiny,
construct a triangle in quad II with x=4 and y = 3
since tanĂ˜ = y/x or opposite/adjacent
so r^2 = (4)^2 + 3^2
r = 5
sinx = 3/5 and cosx = 4/5
you have to know that
sin 2x = 2sinxcosx = 2(3/5)(4/5) = 24/25
cos 2x = cos^2 x  sin^2 x = 16/25  9/25 = 7/25
tan 2x = sin 2x/ cos 2x = (24/25) / (7/25) = 24/7