【两个有趣的积分】解答篇

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  • (此解法来自渡鸦)

记 \( I=\int_{0}^{1}\log\sin(\pi t)dt \)

根据积分换元公式,设 \( u=2t \) ,有

$$ \begin{split} I &= \int_0^{1/2}2\log\sin(2\pi u)du\\ &= 2\int_0^{1/2}\log(2\sin(\pi u)cos(\pi u))du\\ &= \log2 + 2\int_0^{1/2}\log\sin(\pi u)du + 2\int_0^{1/2}\log\cos(\pi u)du \end{split} $$ 继续阅读“【两个有趣的积分】解答篇”