三角降次公式

參考 > 微積分學: 積分法

描述

sinnxdx=1nsinn1xcosx+n1nsinn2xdx\int \sin^{n}x \, dx=-\frac{1}{n}\sin^{n-1}x\cos{x}+\frac{n-1}{n}\int \sin^{n-2}x \, dx

cosnxdx=1ncosn1xsinx+n1ncosn2xdx\int \cos^{n}x \, dx=\frac{1}{n}\cos^{n-1}x\sin{x}+\frac{n-1}{n}\int \cos^{n-2}x \, dx

tannxdx=1n1tann1xtann2xdx\int \tan^{n}x \, dx=\frac{1}{n-1}\tan^{n-1}x-\int \tan^{n-2}x \, dx

cotnxdx=1n1cotn1xcotn2xdx\int \cot^{n}x \, dx=-\frac{1}{n-1}\cot^{n-1}x-\int \cot^{n-2}x \, dx

secnxdx=1n1secn2xtanx+n2n1secn2xdx\int \sec^{n}x \, dx=\frac{1}{n-1}\sec^{n-2}x\tan{x}+\frac{n-2}{n-1}\int \sec^{n-2}x \, dx

cscnxdx=1n1cscn2xcotx+n2n1cscn2xdx\int \csc^{n}x \, dx=-\frac{1}{n-1}\csc^{n-2}x\cot{x}+\frac{n-2}{n-1}\int \csc^{n-2}x \, dx


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