Suppose we have complex number $z=a+i b$, where $a$ and $b$ are variables.
Now, if we want real part of $z$, then in mathematica we use
Re[z] command. But this command is not working (because $a$ and $b$ are not fixed real numbers).
Re[expr] is left unevaluated if expr is not a numeric quantity. (https://reference.wolfram.com/language/ref/Re.html)
How do we get
Re[z]$=a$ as solution?