Proving Angle
Relationships
Section 2-8
Protractor Postulate
Given AB and a number r
between 0 and 180, there is exactly
one ray with endpoint A, extending
on either side of AB , such that the
measure of the angle formed is r.
Angle Addition Postulate
If R is in the interior of PQS
, then mPQR  mRQS  mPQS.
Converse is also true.
P
R
Q
S
Supplement Theorem (2.3)
If
2 angle form a linear pair,
then they are supplementary
angles.
120
60
Complement Theorem (2.4)
If
the noncommon sides of 2
adjacent angles form a right
angle, then the angles are
complementary angles.
Theorem 2-5
Congruence of angles is
reflexive, symmetric, and
transitive.
A  A
If A  B then B  A
If A  B and B  C then
A  C
Theorems 2-6 and 2-7
 Angles
supplementary to the same
angle or to congruent angles are
congruent.
 Angles
complementary to the same
angle or to congruent angles are
congruent.
Theorems 2.8 - 2.13
 All
right angles are congruent.(2.10)
 Vertical angles are congruent.(2.8)
140
40
40
140
 Perpendicular
lines intersect to form 4
right angles. (2.9)
 Perpendicular
lines form congruent
adjacent angles. (2.11)
 If 2 angles are congruent and
supplementary, then each angle is a
right angle. (2.12)
 If 2 congruent angles form a linear pair,
then they are right angles.
Joke Time
Why do bees have sticky
hair?
Because they have
honeycombs!
What goes Oh, Oh, Oh?
Santa walking backwards.