why does Matlab not expand(abs(a-b)^2) ?

Wolfram alpha shows: a^2 -2*a*b+b^2

Answer 1

[Walter Roberson]

>> a=complex(rand,rand)

a =

         0.0975404049994095 +     0.278498218867048i

>> b=complex(rand,rand)

b =

          0.546881519204984 +     0.957506835434298i

>> abs(a-b)^2

ans =

         0.662960138288077

>> a^2-2*a*b+b^2

ans =

         -0.259145264457063 +     0.610212976647027i

[Niklas Kurz]

Hence it's incorrect for complex numbers. Alrigth. But for real numbers it should work. However

expand(abs(real(a)-real(b))^2

still doesn't expand.

[Walter Roberson]

expand(simplify(abs(real(a) -real(b) ) ^2))