Answer
{0, -1, 0, 1, 0}
Work Step by Step
Plug in $n$ = 1:
$a_{1}=cos\frac{(1)\pi}{2} =0$
Plug in $n$ = 2:
$a_{1}=cos\frac{(2)\pi}{2} =-1$
Doing the same for $n = 3,4,5:$
$a_{3}=cos\frac{(3)\pi}{2} =0$
$a_{4}=cos\frac{(4)\pi}{2} =1$
$a_{5}=cos\frac{(5)\pi}{2} =0$
Therefore, the first 5 terms of the sequence are:
{0, -1, 0, 1, 0}