# Real and imaginary

1. Aug 20, 2004

Hey,
I was wondering if anyone could explain to me the meaning of "real and imaginary parts of a complex signal"?

Thanks
Jay

2. Aug 20, 2004

### cronxeh

im gonna ignore the signal part..

but in a form of say z = a + ib where i= $$\sqrt{-1}$$

the a is the real part, and
the ib is the imaginary

3. Aug 20, 2004

### robphy

In some textbooks, the "Imaginary Part of z" is defined Im(z)=b, a real number.
So, z=Re(z)+i Im(z).

Using the notation z* for the "complex-conjugate of z"...
To determine Re(z) from z, use Re(z)=(z+z*)/2.
To determine Im(z) from z, use Im(z)=(z-z*)/2i.

4. Aug 20, 2004

laymen

What I failed to mention was that I have a very low understanding of math. Could you explain that again in laymen terms.

Thanks
Jay

5. Aug 20, 2004

### chroot

Staff Emeritus
If you can provide us some context for where you read this quote, we can probably be more helpful. Normally complex numbers are used to simplify the mathematical treatment of engineering problems, but all physically possible signals are real only.

- Warren

6. Aug 20, 2004

### Simfish

In the complex number system, there are two axes: the horizontal real axis and the vertical imaginary axis. The imaginary part of a number can be ositioned along the imaginary axis.