Answer:

Step-by-step explanation:
we know that
The area of the shaded region is equal to the area of the sector minus the area of the triangle
step 1
Find the area of the circle
the area of the circle is equal to

we have

substitute


step 2
Find the area of the sector
we know that
The area of the circle subtends a central angle of 360 degrees
so
by proportion find out the area of a sector by a central angle of 72 degrees

step 3
Find the area of triangle
The area of the triangle is equal to

step 4
Find the area of the shaded region
Subtract the area of the triangle from the area of the sector
