Answer:
Option D. The student did not use the correct formula to calculate the area of the segment
Explanation:
step 1
Find the area of the isosceles triangle
Applying the law of sines

step 2
Find the area of the sector
The area of the sector is 1/6 of the area of the circle
so

substitute the value

step 3
Find the area of the segment
The area of the segment is equal to the area of sector minus the area of triangle

therefore
The student did not use the correct formula to calculate the area of the segment