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-   -   Proving Trig Identities (https://www.askmehelpdesk.com/showthread.php?t=300669)

  • Jan 7, 2009, 08:27 PM
    angemnn227
    Proving Trig Identities
    How would I prove an Identity like the cos(2x)=1-2(sinx)^2 or something like sin(2x)=2sinx*cosx. I don't really know how to get started
  • Jan 8, 2009, 01:31 PM
    galactus
    To prove use the addition formula for sine.



    Then, we can write

    and get:



    See there?

    To prove







    Easier than you thought, huh?

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