çï¼ä¾å¦:æ±ï¼[1-(tanx)^2]/sin(2x) çä¸å®ç§¯åã
â«[1-(tanx)^2]dx/sin2x=â«[1-(tanx)^2]dx/{(2tanx)/[1+(tanx)^2]}=â«[1-(tanx)^4]dx/(2tanx)
=(1/2)â«cotxdx-(1/2)â«tanx[1-(cosx)^2](cosx)^2]dx=(1/2)[â«dsinx/sinx-â«tanxdtanx-â«dcosx/cosx]
=(1/2)[ln|sinx|-ln|cosx|-(1/2)(tanx)^2]+C
=(1/2)ln|tanx|-(1/4)(tanx)^2+Cã
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