How to simply differentiate equations?

I have defined an equation V(x,t), can i store the second derivitive of this equation in a new equation?

Answer 1

[Wayne King]

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

[Joe Koning]

so now d2V_dx2 is a function of x,t? How would i then sub in values of x and t?

[Wayne King]

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])