tanθ=sinθ/cosθ=2即cosθ=sinθ/2代入sin^2θ+cos^2θ=15/4*sin^2θ=1sin^2θ=4/5sinθ=+-(2√5)/5
sin/cos=2cos=sin/2sin^2+(sin/2)^2=1sin^2=4/5sin=+/-2根5/5
sinθ/cosθ+1/cosθ=5cosθ=√1-(sinθ)^2得出sinθ=1或者12/13