∫(x-2)√(4-x^2)dx
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∫(x-2)√(4-x^2)dx
![∫(x-2)√(4-x^2)dx](/uploads/image/z/2037060-36-0.jpg?t=%E2%88%AB%28x-2%29%E2%88%9A%EF%BC%884-x%5E2%EF%BC%89dx)
4-x²=2²-x²,令x=2sinu则dx=2cosudu,sinu=x/2
√(4-x²)=√(4-4sin²u)=2cosu,cosu=(1/2)√(4-x²)
∴∫(x-2)√(4-x²) dx
=∫(2sinu-2)2cosu*2cosu du
=8∫(sinu-1)cos²u du
=8∫sinucos²u du-8∫cos²u du
=-8∫cos²u d(cosu)-4∫(1+cos2u) du
=(-8/3)cos³u-4(u+1/2*sin2u)+C
=(-8/3)[1/2*√(4-x²)]³-4arcsin(x/2)-4*x/2*(1/2)√(4-x²)+C
=(-1/3)(4-x²)^(3/2)-4arcsin(x/2)-x√(4-x²)+C
√(4-x²)=√(4-4sin²u)=2cosu,cosu=(1/2)√(4-x²)
∴∫(x-2)√(4-x²) dx
=∫(2sinu-2)2cosu*2cosu du
=8∫(sinu-1)cos²u du
=8∫sinucos²u du-8∫cos²u du
=-8∫cos²u d(cosu)-4∫(1+cos2u) du
=(-8/3)cos³u-4(u+1/2*sin2u)+C
=(-8/3)[1/2*√(4-x²)]³-4arcsin(x/2)-4*x/2*(1/2)√(4-x²)+C
=(-1/3)(4-x²)^(3/2)-4arcsin(x/2)-x√(4-x²)+C