>Dear math users, >just a simple problem, but I got no answer from thew book. >Re[x + I y] gives >Re[x + I y] >whereas >Re[2 + 3 I] >gives 2 >How could I tell Mathematica that x and y are real numbers?
There is a package <<Algebra`ReIm` that lets you specify that given variables are purely real. Try the following:
Re[x + I y]
Im[x + I y]
Out= x Out= y
The up definitions make the assignment associated with x and y rather than with Im...