MATLAB: What does this upperline mean

Question

I did a simple test.

What does the lines above bs mean?

Answer 1

It indicates that the expression involves the complex conjugate of those elements of b. You didn't tell Symbolic Math Toolbox that b was real, so it has to assume b could be complex. You then use the conjugate transpose operator ' instead of the non-conjugate transpose operator .' so it conjugated b.

syms a
syms b real
withConjugate = [a', b']
withoutConjugate = [a.', b.']