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Topic: complex numbers
Replies: 8   Last Post: Jan 31, 2007 7:33 PM

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Posts: 350
Registered: 1/29/05
complex numbers
Posted: Jan 30, 2007 5:21 PM
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How would i evaluate the following:

1+2w+3w^2+...+nw^n-1, where w is an nth root of unity.

apparently, the solution is: n(n+1)/2 if w= 1

I don't know how they got this? Any hints please?

Also how do i describe a family of curves in the complex plane:

1. Re(1/z)= C

The answer is a family of circles centered at 1/(2C)+0i of radius 1/
modulus 2C but with the origin excluded.

My question is how did they get the center as 1/(2C)+0i and radius 1/
modulus 2C.

I got the Re(1/z)= x/(x^2+y^2) = C but how do i obtain the radius and
the center as indicated above?

I know the equation of a circle is: x^2 +y^2= r^2

Thank you in advance.

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