Question

Which fact helps you prove the isosceles triangle theorem, which states that the base angles of any isosceles triangle have equal measure?

1. The base angles of an equilateral triangle have equal measure
2. if two sides of a triangle are equal, the third side must be equal to the others
3.If a triangle is equiangular, then it is equilateral.
4.If one angle of a triangle is larger than another angle, then the side opposite the larger angle is longer than the side opposite the smaller angle.

Answer 1

4. If one angle of a triangle is larger than another angle, then the side opposite the larger angle is longer than the side opposite the smaller angle.

Explanation:

Facts about equiangular/equilateral triangles have little bearing on isosceles triangles.

The one relevant fact from the given list is that larger angles are opposite longer sides. This requires you to conclude that equal angles are opposite equal sides, which is the conclusion of the isosceles triangle theorem.