求y=(e∧x)sinx的n阶导数 答案是y(n)=e∧x(sinx+sin(x+π/2)+…+s
求y=(e∧x)sinx的n阶导数 答案是y(n)=e∧x(sinx+sin(x+π/2)+…+s
求y=(e∧x)sinx的n阶导数
答案是y(n)=e∧x(sinx+sin(x+π/2)+…+sin(x+nπ/2))
=e∧x((sinx+sin(x+nπ/2))+(sin(x+π/2)+sin(x+(n-1)π/2))+…)
=2∧(n/2) e∧x sin(x+nπ/4)
最后一步是怎么来的