不定积分x^2/(a^2-x^2)^1/2dx
=-积分[a^2-x^2-a^2]/(a^2-x^2)^1/2dx
=-积分(a^2-x^2)^1/2dx+积分a^2/(a^2-x^2)^1/2dx
=-x(a^2-x^2)^1/2-积分x^2/(a^2-x^2)^1/2dx+a^2arcsin(x/a)+C
得不定积分x^2/(a^2-x^2)^1/2dx
=-(x/2)(a^2-x^2)^1/2+(a^2/2)arcsin(x/a)+C