设 x = sinα,则 dx = cosα*dα
∫√(1-x^2) *dx /x^2
=∫cosα * (cosα *dα) /(sinα)^2
=∫(cotα)^2 dα
=∫[(cscα)^2 -1] *dα
=∫(cscα)^2*dα - ∫ dα
=-cotα - α + C
=-√(1-x^2)/x - arcsinα + C