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Math Help - Trig identities

  1. #1
    Newbie Jason2JZ's Avatar
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    Post Trig identities

    How do i Prove this?

    Cos ^2 x - Sin^2 x

    Cos^2 x + SinxCosx

    =1-Tanx
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  2. #2
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    Hello, Jason2JZ!

    Did you try anything?


    Prove: . \frac{\cos^2\!x - \sin^2\!x}{\cos^2\!x + \sin x\cos x}\;=\;1 - \tan x
    Factor and reduce . . .

    . . \frac{(\cos x - \sin x)(\cos x + \sin x)}{\cos x(\cos x + \sin x)} \;=\; \frac{\cos x -\sin x}{\cos x} \;=\;\frac{\cos x}{\cos x} - \frac{\sin x}{\cos x} \;=\;1 - \tan x

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