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



nonton
Posts:
350
Registered:
1/29/05


complex numbers
Posted:
Jan 30, 2007 5:21 PM


How would i evaluate the following:
1+2w+3w^2+...+nw^n1, 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.



