To find the area of a sector of a circle in terms of π having the angle in degrees you use the next formula:

r is the radius
To find area of sector MAG:
1. Find the angle of the sector MAG.
The semicircle has an angle of 180° and it is divided into 3 sectors MAG, GAI, and IAP.
As the arcs MG and IP are congruents (have the same measure) the angles of the sectors MAG and IAP are also congruent.

Use the equation above to find the measure of angle MAG:

2. Find the area of sector MAG:
Angle 75°
radius= half of the diameter (26/2 = 13)
r=13

The exact area of the sector MAG is 845/24 π units squared.
Rounded to the nearest hundredth 35.21 π units squared or 110.61 units squared