∫dx/sinx
=∫sindx/sin²x
=-∫dcosx/(1-cos²x)
=∫dcosx/(cos²x-1)
=1/2∫[1/(cosx-1)-1/(cosx+1)dcosx
=1/2*[ln|cosx-1|-ln|cosx+1|]+C但是跟书上的答案不同继续化简(1-cosx)/(1+cosx)