∫dx/(x²√1-x²) 分部法：u=1/√(1-x²),du=-xdx/√(1-x²),dv=dx/x²,v=-1/x, =-1/[x√(1-x²)] - ∫(1/x)(xdx/√(1-x²) =-1/[x√(1-x²)] - ∫dx/√(1-x²) =-1/[x√(1-x²)] - arcsinx + C
