(3)lim(x->0) ∫(0->x^2) ln(1+t) dt / [x^2.(sinx)^2]=lim(x->0) ∫(0->x^2) ln(1+t) dt / x^4 (0/0 分子分母分别求导)=lim(x->0) 2x.ln(1+x^2) / (4x^3) =lim(x->0) 2x^3 / (4x^3) =1/2
