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Homework Help: Tricky complex numbers problem

  1. Feb 16, 2009 #1
    1. The problem statement, all variables and given/known data

    z1 = 1 + i, z2 = i − 5 are points in the complex plane. If z2 is rotated about z1 by 450
    find its new position.

    Attempt at solution
    Absolutely no idea! I think I might need to use e^theta*i but not sure!
  2. jcsd
  3. Feb 16, 2009 #2
    What does that mean rotated about z1 by 450? Could you elaborate?
  4. Feb 16, 2009 #3
    Sorry, thats all that was given...
    I think it means like rotating 45 degs through the imaginary axis?
  5. Feb 16, 2009 #4
    But then what does that have to do with Z1.
  6. Feb 16, 2009 #5


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    Science Advisor
    Homework Helper

    45 degrees is pi/4 radians. To rotate around another point, find the difference z2-z1 and rotate that by pi/4 (sure, multiply by e^(i*pi/4)). Add the result back to z1.
  7. Feb 16, 2009 #6
    thank you!
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