[iMATLAB]

sym x y
f=sym('u(x,y).*v(x,y)');
diff(f)

想求f的微分，运行出了问题，
??? Error using ==> sym.sym>char2sym at 414
Not a valid symbolic expression.

Error in ==> sym.sym at 95
S = char2sym(x);

Error in ==> diffwrong at 2
f=sym('u(x,y).*v(x,y)');

麻烦大家帮我一个忙，如果把“.*‘改为”*“
结果就出来了
ans =

diff(u(x,y),x)*v(x,y)+u(x,y)*diff(v(x,y),x)

大家分析一下，谢谢了！