sin(3π+θ)=lg1/10^(1/3)=lg10^(-1/3)=-1/3sin(3π+θ)=sin(π+θ)=-sinθ所以sinθ=1/3原式=[-cosθ/[cosθ(-cosθ-1)]+[cosθ/cosθ(-cosθ)+cosθ]=1/(1+cosθ)+1/(1-cosθ)=(1-cosθ+1+cosθ)/sin²θ=2/(1/3)²=18
