What is e^-iPi/2 and how can it be represented using cos and sin notation?

[DiracPool]

If e^iPi/2=i, what does e^-iPi/2 equal? And could you please write it out in cos + sin notation? For some reason I am not geting this. This is not homework, by the way, its come up in an article on spinors I'm reading Thanks.

 

[Klungo]

A simple google check would do the trick.

Anywho, e^(ix)=cos(x)+i*sin(x) for complex variable x.

 

[micromass]

A simple google check would do the trick.

Anywho, e^(ix)=cos(x)+i*sin(x) for complex variable x.

Continuing with this. If x=-\pi /2, then

e^{-i\pi /2}=\cos(-\pi/2)+i\sin(-\pi/2)=-i.

 

[DiracPool]

I got the first one Klungo. Thanks for the follow up micromass. Now I got it, its just like spinning the dial from the top of the complex plane to the bottom.