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 Author Comment/Response jf 04/20/13 8:47pm a) Is f already defined somewhere in your code? Clear[f] before running these inputs would eliminate that possibility. b) DSolve needs both independent variables in the third argument. c) DiracDelta is not a nice function. It would not surprise me if DSolve cannot do much with it. d) That these just echo says DSolve did not know how to solve them. In[1]:= eqns = {Derivative[0, 1][f][x, t] == a*Derivative[2, 0][f][x, t], Derivative[1, 0][f][0, t] == 0, Derivative[1, 0][f][L, t] == 0, f[x, 0] == DiracDelta[x]} In[2]:= DSolve[eqns, f[x, t], {x, t}] Out[2]= DSolve[{f^(0,1)[x, t] == a f^(2,0)[x, t], f^(1,0)[0, t] == 0, f^(1,0)[L, t] == 0, f[x, 0] == DiracDelta[x]}, f[x, t], {x, t}] In[3]:= DSolve[eqns, f, {x, t}] Out[3]= DSolve[{f^(0,1)[x, t] == a f^(2,0)[x, t], f^(1,0)[0, t] == 0, f^(1,0)[L, t] == 0, f[x, 0] == DiracDelta[x]}, f, {x, t}] In[4]:= \$Version Out[4]= 9.0 for Microsoft Windows (64-bit) (January 25, 2013) URL: ,

 Subject (listing for 'BC keeps returning true') Author Date Posted BC keeps returning true darin 04/20/13 10:49am Re: BC keeps returning true jf 04/20/13 8:47pm Re: Re: BC keeps returning true darin 04/21/13 06:50am
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