∫ dx/sinx=∫ dx/(2*sin(x/2)*cos(x/2))=∫ d(x/2)/(sin(x/2)*cos(x/2))=∫ (d(x/2)/cos^2(x/2)) / (sin(x/2)/cos(x/2))=∫ d(tan(x/2)) / tan(x/2)=ln | tan(x/2) | +C有不懂欢迎追问
