# Cartesian , Polar and Exponential Form . Help needed thanks .

1. Sep 28, 2009

### mikecrush

Express -2(cos pai/4+i sin pai/4 ) in Cartesian , Polar and Exponential form ?

how can i convert this : - 2 (cos pai / 4 + i sin pai / 4 ) to Cartesian , Polar and Exponential form ?

Thank you very much

2. Sep 28, 2009

### lanedance

hi mikecrush - any ideas on how to try & solve it?

worth starting by having a look at the definition/properties of complex exponentials

3. Sep 28, 2009

### Elucidus

So the number is $-2(\cos \pi/4 + i \sin \pi/4)$.

Do you know what the definitions of Cartesian, Polar, and Exponential forms are?

You may need the following equations:

$$\begin{array}{c}x=r\cos \theta \\ y=r \sin \theta \\ x^2 + y^2 = r^2 \\ \tan \theta = \frac{y}{x}\\ e^{i \theta} = \cos \theta + i \sin \theta \end{array}$$​

--Elucidus