∫ (x^2*arccosx)dx=x^3/3*arccosx+[(2+x^2)/9]*根号(1-x^2)+C?

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∫ (x^2*arccosx)dx=x^3/3*arccosx+[(2+x^2)/9]*根号(1-x^2)+C?
∫ (x^2*arccosx)dx=x^3/3*arccosx+[(2+x^2)/9]*根号(1-x^2)+C?

∫ (x^2*arccosx)dx=x^3/3*arccosx+[(2+x^2)/9]*根号(1-x^2)+C?
第二项符号似乎不对!
I =∫(x^2*arccosx)dx = (1/3)∫arccosxdx^3
= (1/3)x^3*arccosx + (1/3)∫x^3dx/√(1-x^2),
令 x=sint,则
I1 = ∫x^3dx/√(1-x^2) = ∫(sint)^3dt
= -∫[1-(cost)^2]d(cost) = -cost+(1/3)(cost)^3+3C
= -(1/3)cost[3-(cost)^2]+3C = -(1/3)cost[2+(sint)^2]+3C
= -(1/3)√(1-x^2)(2+x^2)+3C,
则 I = (1/3)x^3*arccosx - (1/9)√(1-x^2)(2+x^2)+C