Answer
$1$
Work Step by Step
Let us consider:
$g(\theta)=\cos \theta$ and $\theta=60^{\circ}$
We know from the unit circle that
$\cos (60^{\circ})=\cos (\dfrac{\pi}{3})=\dfrac{1}{2}$
Thus, we have: $ 2 \ g (\theta)= 2 \times \cos (60^{\circ})
\\=2 \times \cos (\dfrac{\pi}{3}) \\ = 2 \times \dfrac{1}{2} \\=1$