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Thread: Proving trigonometric identities.

  1. December 2nd 2009, 02:59 PM #1
    Skoz
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    Proving trigonometric identities.

    Prove each identity

    a) cosx tan^3x= sinx tan^2x


    do i do

    1-2sin^2x 2tanx/1-tan^2x = sinx tan^2x
    Last edited by Skoz; December 2nd 2009 at 04:25 PM.
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  2. December 2nd 2009, 04:47 PM #2
    skeeter
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    Quote Originally Posted by Skoz View Post
    Prove each identity

    a) cosx tan^3x= sinx tan^2x


    do i do

    1-2sin^2x 2tanx/1-tan^2x = sinx tan^2x ???
    \cos{x} \cdot \tan^3{x} = \cos{x} \cdot \frac{\sin^3{x}}{\cos^3{x}} = \frac{\sin^3{x}}{\cos^2{x}} = \sin{x} \cdot \frac{\sin^2{x}}{\cos^2{x}} = \sin{x} \cdot \tan^2{x}
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