分部积分法公式例题是什么?
分部积分法公式例题:
∫xsinxdx
=-∫xdcosx
=-(xcosx-∫cosxdx)
=-xcosx+∫cosxdx
=-xcosx+sinx+c
∫u'vdx=uv-∫uv'dx。
分部积分:
(uv)'=u'v+uv'
得:u'v=(uv)'-uv'
两边积分得:∫u'vdx=∫(uv)'dx-∫uv'dx。
即:∫u'vdx=uv-∫uv'dx,这就是分部积分公式。
也可简写为:∫vdu=uv-∫udv。
分部积分法定理
定理1:设f(x)在区间[a,b]上连续,则f(x)在[a,b]上可积。
定理2:设f(x)区间[a,b]上有界,且只有有限个间断点,则f(x)在[a,b]上可积。
定理3:设f(x)在区间[a,b]上单调,则f(x)在[a,b]上可积。
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