The circumference and length of the darkened part of the arc are:
Circumference = 18π
Arc length = 18π/5.
In Mathematics and Eulidean Geometry, the circumference of a circle can be calculated by using the following mathematical equation (formula):
C = 2πr
Where:
- C represents the circumference of a circle.
- r represents the radius of a circle.
By substituting the radius, we have:
C = 2π × 9
C = 18π units.
In Mathematics and Geometry, the arc length formed by a circle can be calculated by using the following equation (formula):
Arc length = 2πr × θ/360
Where:
- r represents the radius of a circle.
- θ represents the central angle.
Since the circle is divided into five equal parts, the central angle is given by;
θ = 360/5
θ = 72°
Arc length = rθ
Arc length = 9 × 72 × π/180
Arc length = 9 × 2 × π/5
Arc length = 18π/5