How to simply differentiate equations?

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Joe Koning
Joe Koning 2013-4-24
I have defined an equation V(x,t), can i store the second derivitive of this equation in a new equation?

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Wayne King
Wayne King 2013-4-24
编辑：Wayne King 2013-4-24
Do you have the Symbolic Toolbox?
syms x t;
v = cos(x)*sin(t);
d2v_dx2 = diff(v,'x',2);
d2v_dx2 has class sym
  2 个评论
Joe Koning
Joe Koning 2013-4-24
so now d2V_dx2 is a function of x,t? How would i then sub in values of x and t?
Wayne King
Wayne King 2013-4-24
编辑：Wayne King 2013-4-24
use subs() for example, to leave t alone and put in pi for the x variable
subs(d2v_dx2,[x,t],[pi,t])
or to substitute for both variables
subs(d2v_dx2,[x,t],[pi,pi/2])

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