Error in the determinant line

Error in detA line:

syms Ex Ey Ez c Bx By Bz
A=sym(zeros(4,4));
A=[0 -Ex/c -Ey/c -Ez/c; Ex/c 0 -Bz By; Ey/c Bz 0 -Bx; Ez/c -By Bx 0 ];
detA=det(A);

[James Tursa]

Works for me:

>> detA=det(A)

detA =
(Bx^2*Ex^2)/c^2 + (By^2*Ey^2)/c^2 + (Bz^2*Ez^2)/c^2 + (2*Bx*By*Ex*Ey)/c^2 + (2*Bx*Bz*Ex*Ez)/c^2 + (2*By*Bz*Ey*Ez)/c^2

[John D'Errico]

I wonder if you defined a variable named det?