高等数学,求积分,谢谢
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原式=∫sectdtant
=secttant-∫tantdsect
=secttant-∫secttan^2tdt
=secttant-∫sect(sec^2t-1)dt
=secttant-∫sec^3tdt+∫sectdt
移项得
2∫sec^3tdt=secttant+∫sectdt
=secttant+∫1/costdt
=secttant+∫cost/cos^2tdt
=secttant+∫1/cos^2tdsint
=secttant+∫1/(1-sin^2t)dsint
=secttant+1/2∫[1/(1-sint)+1/(1+sint)]dsint
=secttant-1/2ln[1/(1-sint)]+1/2ln[1/(1+sint)]+C1
=secttant+1/2ln(1-sint)-1/2ln(1+sint)+C1
把2除过来即可
=secttant-∫tantdsect
=secttant-∫secttan^2tdt
=secttant-∫sect(sec^2t-1)dt
=secttant-∫sec^3tdt+∫sectdt
移项得
2∫sec^3tdt=secttant+∫sectdt
=secttant+∫1/costdt
=secttant+∫cost/cos^2tdt
=secttant+∫1/cos^2tdsint
=secttant+∫1/(1-sin^2t)dsint
=secttant+1/2∫[1/(1-sint)+1/(1+sint)]dsint
=secttant-1/2ln[1/(1-sint)]+1/2ln[1/(1+sint)]+C1
=secttant+1/2ln(1-sint)-1/2ln(1+sint)+C1
把2除过来即可
追问
额,你是怎么想到的?
追答
边积分边观察呀,有时候不能看到结果,但按照积分的方法一步步做
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