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Math Help - modulus of -cos2x

  1. #1
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    modulus of -cos2x

    I'm not sure how to prove that the modulus of -cos2x in the range 0<x<pi/2 is less than 1.
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  2. #2
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    You should know that

    -1 \leq -\cos{2x} \leq 1

    so

    |-\cos{2x}| \leq 1.

    You should also find the values for which -\cos{2x} = \pm 1, to show that they occur outside the domain 0 < x < \frac{\pi}{2}.
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