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Math Help - write answer in both rectangular from and polar Q in degre

  1. #1
    Senior Member
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    write answer in both rectangular from and polar Q in degre

    Hi

    I want check my answer

    4 - write answer in both rectangular from and polar Q in degre

    a ) (1 + i ) ( 2+ 2i )
    b ) -2 + 2i
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  2. #2
    MHF Contributor

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    For the first one, you have written (1+ i)(2+ 2i)= 2+ 2i+ 2i+2i^2, which is correct but then you have that equal to 2+ 8i. i^2= -1 so that is equal to 2+ 4i- 2= 4i.

    For the second, the angle, 3\pi/4 is correct but "r" is wrong.
    2^2+ 2^2= 8= 4(2) and so r= \sqrt{4(2)}= 2\sqrt{2}. You have 2.8 which is approximately correct but unless you are specifically told to use a decmal approximation, 2\sqrt{2} is far better.
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