sin theta = 8/17 and theta is in the second quadrant. Find sin(2theta),cos(2theta),tan(2theta) exactly

sin(2theta)

cos(2theta)

tan(2theta)

sin(2theta) would it be 2 x (8/17)

cos(2theta) would be 2 x (15/17)

tan(2theta) would be 2 x (8/17 divided by 15/17)

is this correct? I tried punching that into my homework for as an attempt and it comes back incorrect. Maybe I am not writing the exact answers correctly?

2 answers

sinθ = 8/17 in QII means that
cosθ = -15/17

sin2θ = 2sinθcosθ = 2(8/17)(-15/17)
cos2θ = cos^2θ - sin^2θ = (15/16)^2 - (8/17)^2

tan2θ is of course, sin2θ/cos2θ
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