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Math Help - complex numbers questions help

  1. #1
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    complex numbers questions help

    I have coursework to do and I really want a good mark. This question that i am doing is not giving me nice numbers at the end, so if anyone can tell me what they get to make sure I'm not doing it wrong.

    Q1 Let z = 3+5i and w = 3e^[(3*pi)/4] (w= 3 times e to the power of everything in square brackets)

    Find:
    1)z*w
    2)z/w
    3)z+w

    thanks so much for any help
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Quote Originally Posted by princessamme@hotmail.com View Post
    I have coursework to do and I really want a good mark. This question that i am doing is not giving me nice numbers at the end, so if anyone can tell me what they get to make sure I'm not doing it wrong.

    Q1 Let z = 3+5i and w = 3e^[(3*pi)/4] (w= 3 times e to the power of everything in square brackets)

    Find:
    1)z*w
    2)z/w
    3)z+w

    thanks so much for any help
    Let me guess

    w=3e^[(3i pi)/4]

    Just use the fact that

    e^{ix}=cos(x)+i*sin(x)

    EDIT:

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  3. #3
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    wups ye you were right i did mean 3*pi*i. i did that and got
    w= [(-3*root2)/2] + [i*(3*root2)/2]. is this right? it makes the final answers quite complicated numbers, especially part 3 (z+w)
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  4. #4
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    I think the answer is
    z*w=-3*root2*(4+i)
    z/w=-root2/3*(1-4i)
    z+w=3-3*root2/2+(3*root2/2+5)i
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  5. #5
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    Smile

    Thanks, yeah thoses were the answers i got i just thought they were funny numbers so was just checking
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