Answer: 100°
Step-by-step explanation:
In a triangle, we have three angles that add up to 180 degrees.
In an isosceles triangle, we have the base angles and a vertex angle.
base angle + base angle + vertex angle = 180
In an isosceles triangle, two of the sides are of the same length which tells us that our two bottom base angles are the same.
In this question, we are given a base angle of 40 degrees and we're asked to find the third angle.
base angle + base angle + vertex angle = 180
2(base angle) + vertex angle = 180
2(40) + vertex angle = 180
80 + vertex angle = 180
vertex angle = 100
The value of the third angle is 100 degrees.
