Base angles of an isosceles triangle are congruent. Base angles of an isosceles triangle are complementary. Base angles of an isosceles triangle can be equal to the vertex angle. Base angles of an isosceles triangle are acute.

In an isosceles triangle that has exactly two equal sides, the equal sides are called legs and the third side is called the base. The angle included by the legs is called the vertex angle and the angles that have the base as one of their sides are called the base angles. The vertex opposite the base is called the apex.

The height and the base of the triangle will be the same length since it is a 45-45-90 triangle (isosceles).

Convex polygon

An isosceles right triangle is an isosceles triangle and a right triangle. This means that it has two congruent sides and one right angle. Therefore, the two congruent sides must be the legs. Therefore, we only need one of the three lengths to determine the other two lengths of the sides of an isosceles right triangle.

All isosceles triangles have at least 2 acute angles due to 2 sides are equal. The exterior angle of an equilateral triangle is obtuse. If the perimeter of an equilateral triangle is P, then the length of each of the sides is P/3. All isosceles triangles are equilateral triangles.

All triangles have three angles that must add up to 180 degrees. Two of the angles cannot be obtuse angles because the combined angle measure would over 180 degrees which isn’t possible. Therefore at least two angles have to be acute since that is the only scenario (besides having 3 acute angle) for a triangle to form.

An obtuse triangle must contain an obtuse angle and two acute angles. An equilateral triangle must be 60 degrees in every corner, and thus there are 2+ acute angles. An isosceles triangle can have two angles that are 30 degrees (thus two acute), and a 120 degree angle.

There cannot be any right angles in an obtuse triangle.