Answer:
The red arc has length (3/2) π
Step-by-step explanation:
* Lets revise some rules in the circle
- The measure of any arc = the measure of the central angle
subtended by this arc
- Equal central angles subtended by equal arcs
- The length of the arc is a part from the length of the circle,
it depends on the ratio between the measure of this arc
and the measure of the circle
- The measure of the circle = 360°
- The length of the circle = 2πr
* Lets solve our problem
∵ The measure of the arc = 30°
∴ The measure of its central angle 30°
∴ The central angle of the red arc = 30° by condition of
vertically opposite angles are equal in measures
∴ The measure of the red arc = 30°
- The ratio between measure the arc and the measure
of the circle is 30/360 = 1/12
∴ The arc is 1/12 from the circle
∴ The length of the arc is 1/12 from the length of the circle
∴ Length red arc = (1/12) × 2πr
∵ r = 9
∴ Length red arc = (1/12) × 2 × π × 9 = (3/2) π
* The red arc has length (3/2) π
