Question

I have an arc length of 1/2 how many degrees is that
the circumference of the circle is 45

Answer 1

The arc length is proportional to the angle it makes at the center.
Let x degrees be the angle it makes at the center.
x / arc length = 360 / circumference
x / (1/2) = 360 / 45
2x = 8
x = 4 degrees.

Answer 2

Another way to look at it.

The arc length is (1/2)/45 = 1/90 of the entire circumference

So the central angle is also 1/90 of a full revolution/rotation

(1/90)*(360) = 4 degrees is the central angle