写成∫x cosec^2(x)然后用 ∫v'u = vu - ∫u'v 来积也就是说,设x 为u,cosec^2(x) 为v',那么∫cosec^2(x) = -cot X这样可以写成∫x cosec^2(x) = -xcot (x) +∫cot (x)而cot(x) 又可以写成 cos(x)/sin(x),∫cos(x)/si...