sinx的泰勒展开：sinx=x - x^3/3!+ x^5/5!- x^7/7!…+x^97/97!+O(x^97)f(x) = x^2*sinx =x^3 - x^5/3!+ x^7/5!- x^9/7!…+x^99/97!+O(x^99)f(x)在0处的99阶导数值等于99!*1/97!=99*98=9702