secx的积分公式可用cscx的积分公式得到。推导:因为secx= 1/cosx = 1/sin(x+π/2) = csc(x+π/2)所以∫secxdx=∫csc(x+π/2)d(x+π/2)用★再整理即得。因为cscu=1/sinu =1/(2sinu/2 cosu/2) =1/2(tanu/2)(cosu/2)^2=(secu/2)^2 /2(tanu/2)所以∫cscudu=∫d(tanu/2)/(tanu/2) =Ln |tanu/2 | +C★