4.7 Use Isosceles and Equilateral Triangles
Goal • Use theorems about isosceles and equilateral triangles.
Vocabulary
When an isosceles triangle has exactly two congruent sides, these two sides are the legs. The angle formed by the legs is the vertex angle. The third side is the base of the isosceles triangles. The two angles adjacent to the base are called base angles.
Legs
The legs of an isosceles triangle are the two congruent sides.
Vertex angle
The vertex angle of an isosceles triangle is the angle formed by the legs.
Base
The base of an isosceles triangle is the side that is not a leg.
Base angles
The base angles of an isosceles triangle are the two angles adjacent to the base.
Lesson 7 Examples 1-4
