For the answer to the question above,
the angle of 360 ° → π.d
the angle of x ° → 8π
You make the cross-multiply and you can get:
x * π.d = 8π * 360
x * d = 8 * 360
x = 8 * 360/d → where d = 2r
x = 8 * 360/2r
x = 4 * 360/r → where r = 4.5 cm
x = 4 * 360/4.5
x = 320 °
