# Link between ac voltage and complex notation

#### Brecht

Joined Apr 15, 2009
1
Hi,

I'm a Belgian Commercial Engineering student. I study economics, but we have also some courses together with Civil Engineers. Now I have the course 'electronics', but our background of electronics is much smaller than a civil engineers' background, so it's verry difficult for me to study this course.

I have some problems with the link between ac voltage and the complex notation of it.
When you have a ac voltage of the type (amplitude).sin(ωt+θ) and you write it in complex notation, this notation has two part: a complex part(with sinus) and a real part (with cosinus) . The function I gave is only a sinus function, but the complex notation has a sinus and a cosinus part. Is it possible that the cosinus part in the complex notation isn't really important (doesn't give any extra necessary information), and does the complex notation give all the necessary information (how do you find for exaple the frequency)?

Thank you verry much for your help, I appreciate it alot !
(And sorry for the bad English, I'm not a native speaker)

Brecht