03 Dec, 08:15AM in sunny Singapore!

H2 math (complex no.)

Subscribe to H2 math (complex no.) 4 posts

Please Login or Signup to reply.
  • th3m0ment's Avatar
    137 posts since Oct '03
    • when is apply de moivre? when power of z >3?

      got one question here.

      (1+ z^2) / (1 - z^2) = i

      help?

  • Moderator
    eagle's Avatar
    17,964 posts since Aug '01
    • I don't like de moivre's theorem... I rather use Euler's formula... But they are interchangeable....

      for your question

      1+z^2 = i - iz^2

      rearranging gives u

      z^2 = (-1 + i) / (1 + i) --> pls check

      Using Euler's formula,
      -1 + i = e^(i * 3pi /4) * sqrt(2)
      1 + i = e^(i * pi/4) * sqrt(2)

      hence,

      z^2 = { e^(i * 3pi /4) } / { e^(i * pi/4) }

      z^2 = e^(i * pi/2)

      z = e^(i * pi/4) or -e^(i * pi/4)

      z = 1/sqrt(2) * (1 + i) or z = -1/sqrt(2) * (1 + i) --> pls check also...

  • club18's Avatar
    1,378 posts since Feb '07
    • Originally posted by eagle:
      I don't like de moivre's theorem... I rather use Euler's formula... But they are interchangeable....

      for your question

      1+z^2 = i - iz^2

      rearranging gives u

      z^2 = (-1 + i) / (1 + i) --> pls check

      Using Euler's formula,
      -1 + i = e^(i * 3pi /4) * sqrt(2)
      1 + i = e^(i * pi/4) * sqrt(2)

      hence,

      z^2 = { e^(i * 3pi /4) } / { e^(i * pi/4) }

      z^2 = e^(i * pi/2)

      z = e^(i * pi/4) or -e^(i * pi/4)

      z = 1/sqrt(2) * (1 + i) or z = -1/sqrt(2) * (1 + i) --> pls check also...

      looks chim..
      anw, once u got to,
      z^2=( i - 1 )/( 1 + i )
      factorise to get z^2 = i
      easier..

  • th3m0ment's Avatar
    137 posts since Oct '03
Please Login or Signup to reply.