I have gotten this far:(adsbygoogle = window.adsbygoogle || []).push({});

Using cos(2θ) = 1-tan^{2}θ / 1+tan^{2}θ From a previous question:

Let θ= arctan(x):

cos(2θ) = 1-tan^{2}(arctan(x)) / 1+tan^{2}(arctan(x))

=1-x^{2}/ 1+x^{2}

Where x^{2}cannot equal 0 or a negative number

Have I done this in the right way and if so is this as far as I can simplify it?!

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# Simplify cos(2arctan(x))

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