# Geometry Name ____________________________ Essentials, Day 4

```Geometry
Essentials, Day 4
Today:
ο·
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Name ____________________________
You will learn how to use deductive reasoning to write a two-column proof.
At the end of class you will be able to prove statements about segments, angles, and angle pair relationships.
You will be able to write a two-column proof to justify your steps in solving an algebraic equation.
Postulates:
Theorems:
Proofs:
Points/Lines/Planes Postulates
Postulate
1)
2)
3)
4)
5)
6)
Illustration
Perpendiculars
Def.
Perpendicular
lines
planes
line and a plane
2π₯ + 5 = 30 − 3π₯
5π₯ + 5 = 30
5π₯ = 25
π₯=5
c.
d. π + π(ππ + π) = ππ
Statements
Reasons
π∠1 = π∠3
π∠1 + π∠2 = π∠2 + π∠3
π∠1 + π∠2 = π∠π·π΅πΆ
π∠2 + π∠3 = π∠πΈπ΅π΄
π∠π·π΅πΆ = π∠πΈπ΅π΄
Definition of Congruent Angles – If the measures of two angles are congruent then the angles are
congruent
π∠1 = π∠3
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