求定积分,图中第17题,
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求定积分,图中第17题,
![](http://img.wesiedu.com/upload/0/0b/00bb667c724d77cf82e84d9fc30f7265.jpg)
![](http://img.wesiedu.com/upload/0/0b/00bb667c724d77cf82e84d9fc30f7265.jpg)
![求定积分,图中第17题,](/uploads/image/z/7572873-57-3.jpg?t=%E6%B1%82%E5%AE%9A%E7%A7%AF%E5%88%86%2C%E5%9B%BE%E4%B8%AD%E7%AC%AC17%E9%A2%98%2C)
∫xdx/√((x-a)(b-x))
=∫xdx/((x-a)√((b-x)/(x-a))
=∫[2(b-a)tdt/(1+t^2)^2]/[(b-a)t/(1+t^2)] (令t=√((b-x)/(x-a)))
=2∫dt/(1+t^2) (化简)
=2[arctan(+∞)-arctan(0)]
=2(π/2-0)
=π.
=∫xdx/((x-a)√((b-x)/(x-a))
=∫[2(b-a)tdt/(1+t^2)^2]/[(b-a)t/(1+t^2)] (令t=√((b-x)/(x-a)))
=2∫dt/(1+t^2) (化简)
=2[arctan(+∞)-arctan(0)]
=2(π/2-0)
=π.