[x^2√(1-x^2)]dx
令x=sint,0<t<(pai)/2 进行换元,得:
=(sin^2t*cost)d(sint)
=(sin^2t*cost*cost)dt
=(1/4)sin^2(2t)dt
=(1/4){[1-cos(4t)]/2}dt
因为:4dt=d(4t)
=(1/8)dt-(1/32)cos(4t)d(4t)
=(t/8)-[sin(4t)/32]
因为0<t<(pai)/2
=(t/8)-[sin(4t)/32]|(0到(pai)/2)
=[(pai)/16]
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