matlab求导

在matlab中求导要进行符号运算。

>>syms x;

>>y = x^cos(x);

>>ydot = diff(y, x, 1);%对x求一阶导数

ydot =   x^(cos(x) - 1)*cos(x) - x^cos(x)*log(x)*sin(x)  

>> y2dot = diff(y, x, 2)%求二阶导数，求n阶导数同理。  

y2dot =   cos(x)*(x^(cos(x) - 2)*(cos(x) - 1) - x^(cos(x) - 1)*log(x)*sin(x)) - x^(cos(x) - 1)*sin(x) - log(x)*sin(x)*(x^(cos(x) - 1)*cos(x) - x^cos(x)*log(x)*sin(x)) - x^cos(x)*cos(x)*log(x) - (x^cos(x)*sin(x))/x  

>> subs(ydot, x, pi)%将x = pi带入ydot

ans =

  -0.101321183642338

matlab求导

原文：http://www.cnblogs.com/jiangkejie/p/5929657.html