Question 1070361
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Given that cos x= 1/4 with x in Quadrant IV, find the exact value of cos(2x).

THANKS!
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Use the formula


cos(2x) = {{{2*cos^2(x)-1}}} = {{{2*(1/4)^2-1}}} = {{{2*(1/16)-1}}} = {{{2/16-1}}} = {{{1/8-1}}} = {{{-7/8}}}.


The info "with x in Quadrant IV" is excessive, unnecessary and is not used in the solution.


The result, the answer and the solution would be the same even if x in Quadrant I.
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