I am studying Control Theory from Ogata. My math is a little rusty, so this is a math question about Frequency Domain Analysis.(adsbygoogle = window.adsbygoogle || []).push({});

Check this page - http://www.flickr.com/photos/66943862@N06/6337116280/sizes/l/in/photostream/ [Broken]

I get everything upto Equation 8-4

However I don't get the line after that.

The line "where the constant a can be evaluated from Equation (8-2) as follows"

And they write the value of a.

How is

a = G(s) (ωX) /(s^2 + ω^2).

How do they arrive at this value of a?

Can someone help?

And why did they substitute s = -jω after that?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Frequency Domain Analysis - the math

**Physics Forums | Science Articles, Homework Help, Discussion**