令x=cost,则dx=-sint dt
∫√(1-x^2)/x^2 dx
=∫ sint/(cost)^2·(-sint) dt
=-∫(tant)^2 dt
=-∫[(sect)^2-1]dt
=-∫(sect)^2 dt+ ∫ dt
=-(tant)^2+t+C
=-√(1/x^2-1)+arccosx+C