Sum and Difference Identities · Exercise 38

Use a graph to determine whether the functions are the same or different. If they are the same, show why. If they are different, replace the second function with one that is identical to the first. (Hint: think $2x=x+x.$ )

$f\left(\theta \right)=cos\left(2\theta \right),g\left(\theta \right)=co{s}^2\theta -si{n}^2\theta$

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Algebra and Trigonometry 2e · §9.2 Sum and Difference Identities · Exercise 38