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Math Help - Complex No.s Question (arg)

  1. #1
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    Complex No.s Question (arg)

    Hey, can someone help with the following?

    let z = (1+ sqrt(3)i ) and w = (1+i). Evaluate zw and hence show that cos (7*pi/12) = (1 - sqrt(3))/2*sqrt(2)


    Thanks
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  2. #2
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    By expanding first find zw = (1+\sqrt{3}i)(1+i)
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  3. #3
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    Quote Originally Posted by Bushy View Post
    By expanding first find zw = (1+\sqrt{3}i)(1+i)
    oh i can do that with no problems. Its just the 2nd part I need help with.
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  4. #4
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    Quote Originally Posted by noobonastick View Post
    oh i can do that with no problems. Its just the 2nd part I need help with.
    Good! What did you get? And do you know how to use "polar form" to multiply two complex numbers? The argument of that product is equal to the sum of the arguments of the two numbers. And, of course, r cos(\theta) is the real part of the number with modulus r and argument \theta.
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  5. #5
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    Oh Thanks! I solved it.
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