complex conjugate

[shahar]

Why are we multiple the complex number by its complex conjugate?
Why aren't we choose another (complex) number?

 

[Dr.Peterson]

Why are we multiple the complex number by its complex conjugate?
Why aren't we choose another (complex) number?

You mean, why do we multiply a complex number by its complex conjugate, rather than by some other number?

The answer depends on what you are doing! What is the context of your question?

But doing this results in a real number, so we typically do this when that is our goal -- for example, when there is a complex number in the denominator, and we want to change it to a real number. This is how we divide one complex number by another, and might be used in other situations as well.

This is similar to "rationalizing the denominator" in a fraction, where the goal is to eliminate the radical.

 

[shahar]

You mean, why do we multiply a complex number by its complex conjugate, rather than by some other number?

The answer depends on what you are doing! What is the context of your question?

But doing this results in a real number, so we typically do this when that is our goal -- for example, when there is a complex number in the denominator, and we want to change it to a real number. This is how we divide one complex number by another, and might be used in other situations as well.

This is similar to "rationalizing the denominator" in a fraction, where the goal is to eliminate the radical.

Thanks, I mean in fraction made of 2 complex numbers that one divides the another.
Thanks. I understand now.