Express cos(2x) in the form acos^2(x) + b, where a and b are constants.
we first remember the double angle formula, a really important formula. cos(2x) = cos2(x) - sin2(x).We know that sin2(x) + cos2(x) = 1, therefore, cos(2x) = cos2(x) + cos2(x) - 1. Giving our final answer to be, cos(2x) = 2cos2(x) - 1.
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