Download Theorem List (Chapter 4).

GEOMETRY THEOREMS – CHAPTER 4
T4.1: The sum of the measures of the interior angles of a triangle is
.
Triangle Sum Theorem (pg 218)
Corollary: The acute angles of a right triangle are
. (pg 220)
T4.2: The measure of an exterior angle of a triangle is equal to the sum of the measures of the
two
. Exterior Angle Theorem (pg 219)
T4.3: If two angles in one triangle are congruent to two angles in another triangle, then the
third angles are
. Third Angles Theorem (pg 227)
T4.4: Triangle congruence is reflexive, symmetric, and transitive.
REFLEXIVE: For any ABC , ABC  ABC .
SYMMETRIC:
If ABC  DEF , then DEF  ABC .
TRANSITIVE:
If ABC  DEF and DEF  JKL , then ABC  JKL .
Properties of Triangle Congruence (pg 228)
T4.5: If the hypotenuse and a leg of a right triangle are congruent to the hypotenuse and a leg
of a second right triangle, then the two triangles are
.
Hypotenuse-Leg (HL) Congruence Theorem (pg 241)
T4.6: If two angles and a non-included side of one triangle are congruent to two angles and
the corresponding non-included side of a second triangle, then the two triangles
are
.
Angle-Angle-Side (
AAS) Congruence Theorem
(pg 249)
T4.7: If two sides of a triangle are congruent, then the angles opposite them are
.
Base Angles Theorem (pg 264)
Corollary: If a triangle is equilateral, then it is
. (pg 265)
T4.8: If two angles of a triangle are congruent, then the sides opposite them are
.
Converse of the Base Angles Theorem (pg 264)
Corollary: If a triangle is equiangular, then it is
. (pg 265)
(Have you proved it? If you prove any theorem, you should put a  by the theorem and keep the proof in your notes.)