Download Vocabulary - Hartland High School

Section 4.7 Use Isosceles and Equilateral Triangles
Goal  Use theorems about isosceles and equilateral triangles.
Isosceles Triangle: Has at least two congruent sides
Vertex Angle
Leg
Leg
Base Angles
Base
THEOREM 4.7: BASE ANGLES
THEOREM
If two sides of a triangle are congruent,
then the angles opposite them are congruent.
THEOREM 4.8: CONVERSE OF BASE
ANGLES THEOREM
If two angles of a triangle are congruent,
then the sides opposite them are congruent.
If AB  AC , then B  C.
If B  C, then AB  AC
Example 1: In FGH, GH  FH . Name two congruent angles.
COROLLARY TO THE BASE ANGLES
THEOREM
If a triangle is equilateral, then it is
EQUIANGULAR.
THEOREM 4.8: CONVERSE OF BASE
ANGLES THEOREM
If a triangle is equiangular, then it is
EQUILATERAL.
Example 2: Find the measures of R, S, and T.
Example 3: Find the length of the sides and the measures of the angles in the figure below.
Give the perimeter of the triangle.
3x
2x + 10
Section 4.7 Use Isosceles and Equilateral Triangles
Example 4: Find the values of x and y in the diagram.
a.
b.
(2y + 16)º
Checkpoint
Use the information in the diagram to find the given values.
1. Find WY.
2. Find mWXY.
3. Find all the angle measures in the figure below!