Answer
$y=2x-2\pi.$
Work Step by Step
$u=2x$; $\dfrac{du}{dx}=2$
$\dfrac{d}{du}f(u)=\cos{u}$
$\dfrac{d}{dx}f(x)=\dfrac{d}{du}f(u)\times\dfrac{du}{dx}=2\cos{2x}.$
$f'(\pi)=2\cos{2\pi}=2.$
Equation of tangent:
$(y-y_0)=m(x-x_0)$ at point $(x_0, y_0)$ and slope $m$.
$(y-0)=2(x-\pi)\rightarrow y=2x-2\pi.$
A graphing calculator and a computer algebra system have been used to confirm these results.