Pre-Calc

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Prove: 2 - sec^x / 1+ tan ^x = cos 2x

  • Pre-Calc -

    I assume you mean

    (2-sec^2 x)/(1+tan^2 x)
    since sec^2 x = 1+tan^2 x, we have

    (1-tan^2 x)/(sec^2 x)
    multiply top and bottom by cos^2 x
    = (cos^2 x - sin^2 x)/1
    = cos(2x)

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