先对分子做变换∫[0→x] sin(xt)^2 dt令xt=u,则dt=du/x,u：0→x^2=∫[0→x^2] sin(u^2) du /x则原极限化为：lim[x→0] ∫[0→x^2] sin(u^2) du / x^6洛必达法则=lim[x→0] 2xsin(x^4) / (6x^5)=lim[x→0] 2x^5 / (6x...