cosθ=-3/5,角θ在（π/2,π）求2/cos（π/2-θ）+2cos（π-θ）sin(13/6π)/sinθ的值,
问题描述：
cosθ=-3/5,角θ在（π/2,π）求2/cos（π/2-θ）+2cos（π-θ）sin(13/6π)/sinθ的值,
cosθ=-3/5,角θ在（π/2,π）求2/cos（π/2-θ）+2cos（π-θ）sin(13/6π)/sinθ的值
答
cosθ=-3/5,角θ在（π/2,π）sinθ>0sinθ=√(1-cos^2θ=4/52/cos(π/2-θ)+2cos(π-θ)sin13π/6/sinθ=2/sinθ-cosθsinπ/6/sinθ=[2-1/2(cosθ)]/sinθ=[2+(3/5)*1/2]/(4/5)=(23/10)/(4/5)=23/8一直求不出sina,谢谢你的回答 不过好像错了