The arc length can be determined with this formula. arc length = central angle/360° × perimeter of circle.
First, find the perimeter of the circle. p = 2 × π × r. p = 2 × 3.14 × 8. p = 50.24 m.
Second, find the arc length. arc length = central angle/360° × perimeter of circle. arc length = 45°/360° × 50.24.
That is just an explanation of how to do it which that may get you to your answer.