The bisector of the vertex angle of an isosceles triangle is the perpendicular bisector of the base. If a triangle is equiangular, then the triangle is equilateral
If two angles of a triangle are congruent, then the sides opposite the angles are congruent.Ĭorollary to Converse of the Isosceles Triangle Theorem Theorem 4-4 Converse of the Isosceles Triangle Theorem If a triangle is equilateral, then the triangle is equiangular. If two sides of a triangle are congruent, then the angles opposite those sides are congruent. If two angles and a nonincluded side of one triangle are congruent to two angles and the corresponding nonincluded side of another triangle, then the triangles are congruent. Theorem 4-2 Angle-Angle-Side (AAS) Theorem If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the two triangles are congruent. Postulate 4-3 Angle-Side-Angle (ASA) Postulate If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the two triangles are congruent.
Postulate 4-2 Side-Angle-Side (SAS) Postulate If the three sides of one triangle are congruent to the three sides of another triangle, then the two triangles are congruent. Postulate 4-1 Side-Side-Side (SSS) Postulate If the two angles of one triangle are congruent to two angles of another triangle, then the third angles are congruent.