设f(x)=∫x0sintπ-tdt.计算∫π0f(x)dx
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发布时间:2024-10-06 10:16
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时间:2024-10-06 10:20
∫π0f(x)dx
=xf(x)|π0-∫π0xf'(x)dx
又因为:xf(x)|π0=πf(π)-0f(0)=π∫π0sintπ-tdt
f'(x)=(∫x0sintπ-tdt)'=sinxπ-x
所以:∫π0f(x)dx
=xf(x)|π0-∫π0xf'(x)dx
=π∫π0sintπ-tdt-∫π0xsinxπ-xdx
=π∫π0sintπ-tdt-∫π0tsintπ-tdt
=∫π0(π-t)sintπ-tdt
=∫π0sintdt
=-cost|π0
=2.