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Math Help - evaluating complex numbers

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    evaluating complex numbers

    evaluate sqrt(-3)*sqrt(-12)
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    Re: evaluating complex numbers

    Quote Originally Posted by angelamonique View Post
    evaluate sqrt(-3)*sqrt(-12)
    In many modern treatments, we agree that \sqrt{-3} in not defined.
    However we can enlarge the number system by one symbol. We say that i is a solution for x^2+1=0.
    In effect we now have i^2=-1. Now we can say \sqrt{-3}=\sqrt{3}\;i.

    So now your question becomes (\sqrt{3}\;i)(\sqrt{12}\;i)=-\sqrt{36}
    Last edited by Plato; June 25th 2013 at 10:19 AM.
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    Re: evaluating complex numbers

    is it 15i^2 ?
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    Re: evaluating complex numbers

    ohhh thanks!!
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    Re: evaluating complex numbers

    So now your question becomes
    wait, i get the i-part but i don't see how you got 24. isn't sqrt(3)*sqrt(12) = sqrt(3*12) ?
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    Re: evaluating complex numbers

    Aside from the arithmetic mistake, Plato was correct. Express the radicals in terms of i and simplify. \sqrt{-3}\sqrt{-12} = i\sqrt{3}\,\,i\sqrt{12} = i^2\sqrt{36} = -6 Recall that i^2 = -1
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