matlab's out of memory error - matlab

Question

I try to run the following code on matlab:
syms a c mu epsi real
epsi=10
eq_1=(0.5*pi^2-mu+2*epsi)*a+2*epsi*c-0.25*(3*a^3+3*a^2*c+6*a*c^2);
eq_2=(4.5*pi^2-mu+2*epsi)*c+2*epsi*a-0.25*(a^3+6*a^2*c+3*c^3);
[a_mu c_mu ]=solve(eq_1,eq_2,a,c)
N_prime=diff(0.5*(a_mu.^2+c_mu.^2),mu)
and I get the following error:
??? Error using ==> eq
Out of memory. Type HELP MEMORY for your options.
Error in ==> sym.sym>char2sym at 377
if isempty(x) || all(x == ' ') || strcmp(x,'{}')
Error in ==> sym.sym at 95
S = char2sym(x);
Error in ==> sym.maple at 92
result = sym(result,'keepijalias');
Error in ==> sym.diff at 50
R = reshape(maple('map','diff',S(:),x),size(S));
Error in ==> Untitled4 at 10
N_prime=diff(0.5*(a_mu.^2+c_mu.^2),mu)
how can I solve it?