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Warm-Up 9/4/2014
Write the converse and inverse of each
statement, and tell whether each related
statement is true or false (and why):
If x > 4, then x >0
If x < 6, then -x < -6
Chapter 2 – Logic, Postulates,
and Proofs
Tue
9/2 – 2.2 – Conditional Statements
Thu
9/4 – 2.4, 2.5, & 2.6 – Postulates, Algebra, and
Proving Statements about Segments and Angles
Fri
9/5 – More 2.6
Mon
9/8 – 2.7 – Proving Angle Pair Relationships
Tue
9/9 – Review of Chapter 2
Thu
9/11 – Chapter 2 Quiz, Start on Ch. 3
Lessons 2.4-2.6
Use postulates and
properties for proofs
Objectives
• Use postulates involving lines, points, and
planes, as well as algebraic properties, in
logical arguments of geometric properties
What is a postulate?
• A rule that is not proven.
Point, Line, and Plane Postulates
Perpendicular Figures
“line perpendicular to a plane”
• A line is perpendicular to a plane if and only if
the line intersects the plane in a point and is
perpendicular to every line in the plane that
intersects it at that point.
Book Work (as a class)
• Pg. 99-100 #11-23
Algebraic Properties
Algebraic Properties of Equality
More Properties of Equality
More Properties
Proofs
• A series of logical statements that lead us to a
final place.
Proof
• Solve:
2x + 5 = 20 - 3
Proof
• Page 114 in the book, under “Concept
Summary”
• Always start by
– Identifying what is “given”
– Identifying your goal (i.e. what they want you to
“prove”)
Homework
• p.99 #5, 6, 8
• p.108 #3, 4, 7, 9, 11, 13, 35