Answer:
40 degrees
Step-by-step explanation:
Since we have the diameter included in the triangle, the angle at B is 90
This is because angle at center is two times the angle at the circumference
Since we have the diameter, the angle at the center will be 180 degrees so the angle A at the circumference will be 90 degrees
Now, let us use the measure of the arc given
The angle at C is half of 100 which makes it 50
This is according to an angle arc relationship
Lastly, the sum of angles in a triangle is 180 degrees
We already have two angles and we need the last
so we have to add what we have already and subtract from 180 to get the angle we are looking for
So we have the angle as 180-(90 + 50) = 180 -140 = 40
