# Complex number in exponential form

• May 17th 2010, 06:39 PM
acc100jt
Complex number in exponential form
I have one question here regarding complex number in exponential form,

Is the following statement true?

$e^{i\frac{-\pi}{2}}=e^{i\frac{3\pi}{2}}$

Some ppl say that their power series are not equal, so the statement is wrong.

But to me, it seems like they are equal, right?

Anyone can clarify my doubt? Thanks!!!
• May 17th 2010, 06:59 PM
tonio
Quote:

Originally Posted by acc100jt
I have one question here regarding complex number in exponential form,

Is the following statement true?

$e^{i\frac{-\pi}{2}}=e^{i\frac{3\pi}{2}}$

Some ppl say that their power series are not equal, so the statement is wrong.

But to me, it seems like they are equal, right?

Anyone can clarify my doubt? Thanks!!!

Of course they're equal: for real $\phi\,,\,\theta\,,\,\,e^{i\phi}=e^{i\theta}\iff \phi -\theta=2k\pi\,,\,k\in\mathbb{Z}$.

This follows at once from the definition of $e^{ix}\,,\,x\in\mathbb{R}$ , and the periodicity of the trigonometric functions sine and cosine.

Tonio