>>715
sin(2θ) = 2 (cosθ)(sinθ) = -5/12 < 0
tanθ = (sinθ)/(cosθ) = { (cosθ)(sinθ)}/{(cosθ)^2} < 0

cos(2θ) = 2 (cosθ)^2 -1 =12/13
(cosθ)^2 = 25/26

1+(tanθ)^2 = 1/(cosθ)^2 = 26/25
(tanθ)^2 = (1/5)^2
tanθ = -1/5