# Polar form of complex numbers

1. Apr 4, 2017

### Mrencko

1. The problem statement, all variables and given/known data
well this is not exactly a homework, i had an argument whith my teacher about my grade in a test, because i put a complex number in the form of R,theta and she claims that the form was costheta+isentheta, and i know that but i need to prove in a book that r,theta=costheta+isentheta

2. The attempt at a solution
she ditnt request, a solution or demostration just if someone knows a book about the fact, please help me, the matter is from a very good grade to a failure grade so this is important, thank you

i truly believe i am right but the teacher want to screw me really bad and asked for evidence in a book

2. Apr 4, 2017

### FactChecker

The correct equality would be r⋅e = r⋅(cos(θ)+i sin(θ)).
I'm not sure exactly what you were asked for on the test.

3. Apr 4, 2017

### Staff: Mentor

r,theta=costheta+isentheta makes no sense. As @FactChecker already said, the correct identity is $re^{i\theta} = r(\cos(\theta) + i\sin(\theta))$