Answer
$-e^{2t-2\pi} \cos t$
Work Step by Step
We are given that $f(t)=e^{2t}$ and $a=\pi$
When $a$ has a positive value then , shift the function to the right for $a$ units and when $a$ has a negative value then , shift the function to the left for $a$ units
Now, $f(t-a) =f(t-\pi) \\=e^{2(t-\pi)}\cos (t-\pi) \\=-e^{2t-2\pi} \cos t$
