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Math Help - help with trigonometry

  1. #1
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    help with trigonometry

    Can someone help explain this trigonometry equation to me with a detailed development?

    sin2a - cos2a = 1-2 x cos2a


    thank you!
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  2. #2
    MHF Contributor ebaines's Avatar
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    Re: help with trigonometry

    One of the most basic identities to memorize because you will use it frequently is:  \sin^2a + \cos^2a = 1. Rearrange this to get the  \sin^2a by itself, and then substitute for the \sin^2a term in your equation - what do you get? By the way, you could also have replaced the  \cos^2a term in your equation to get a different form of the same equation, all of which are equal to  \cos(2a).
    Last edited by ebaines; October 23rd 2013 at 12:39 PM.
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  3. #3
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    Re: help with trigonometry

    thank you.
    but can you or someone else explain even clearer how to develop and explain the equation, i'm new to maths and trigonometry and really need a full explanation as detailed as possible!
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  4. #4
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    Re: help with trigonometry

    Quote Originally Posted by nova23 View Post
    thank you.
    but can you or someone else explain even clearer how to develop and explain the equation, i'm new to maths and trigonometry and really need a full explanation as detailed as possible!
    \sin^2(x)=1-\cos^2(x) so just substitute on the LHS.
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