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Geometry 2.8 Notes
Laws/Postulates/Theorems to Use in Proofs
Name of Law
Postulate 2.10
Protractor Postulate
•
Given ray AB and a number r
between 0 and 180, there is
exactly one ray with
endpoint A extending on
either side of ray AB, such
that the measure of the
angle formed is r.
Postulate 2.11
Angle Addition Postulate

If R is in the interior of
PQS, then mPQR +
mRQS = m PQS.
Theorem 2.3
Supplement Theorem
•
If two angles form a linear
pair, then they are
supplementary angles.
Theorem 2.4 Complement
Theorem
•
If the non-common sides of
two adjacent angles form a
right angle, then the angles
are complementary angles.



Reflexive
Symmetric
Transitive
•
Angles supplementary to the
same angle or to congruent
angles are congruent.
Theorem 2.5
Properties of Angle
Congruence
Theorem 2.6
Congruent Supplements
Theorem
Statement of Law
Example/Sketch
Theorem 2.7
Congruent Complements
Theorem
Theorem 2.8
Vertical Angles Theorem
•
Angles complementary to
the same angle or to
congruent angles are
congruent.
•
If two angles are vertical
angles, then they are
congruent.
•
Perpendicular lines intersect
to form four right angles.
•
All right angles are
congruent.
•
Perpendicular lines form
congruent adjacent angles.
•
If two angles are congruent
and supplementary, then
each angle is a right angle.
•
If two congruent angles form
a linear pair, then they are
right angles.
Theorem 2.9
Theorem 2.10
Theorem 2.11
Theorem 2.12
Theorem 2.13