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Ch. 3
3.2 Lines & Angles
HMWK:
p. 139, #s 11 – 24, you have all weekend for this
assignment … take your time on the proofs and you will be fine.
Game Plan: Today I will be able to prove results
about perpendicular lines, using different proof
methods.
Warm-Up:
Ch. 3
3.2 Lines & Angles
Today …
1.
2.
3.
4.
5.
Constructions worksheet
Flow proof activity
GSP activity
Notes
Wrap up.
Ch. 3
3.2 Lines & Angles
Flow Proofs
 Third type of proof
 Uses visual method
 Complete activity in book with same partners
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
P. 135
Under exploring the concept
Cut and paste statements instead of rewriting
 15 minutes to complete

Ch. 3
3.2 Lines & Angles
Types of Proofs
1. List the three types of proofs we have studied
2. Explain how to write each proof. Be sure to
include similarities and differences.
Answers:
1. Two-column, paragraph, flow proof
2. How to write …
• Statements/Reasons in chronological, sequential order
• Complete sentences explaining proof
• Uses arrows & boxes to show the “flow” of the proof
Ch. 3
3.2 Lines & Angles
Sketch Pad Activity
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•
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Groups of four.
Use Geometer’s Sketchpad to complete experiment
Be sure all answers are typed on the “sketch”
Be sure to have all group members name on your
work
• You will have 20 minutes to complete this activity
•
I strongly suggest you use your time wisely …we have
been having a problem in this area.
Ch. 3
3.2 Lines & Angles
Theorems
Thm 3.1: If two lines intersect to form a linear
pair of congruent angles, then the lines are
perpendicular.
diagram…
Ch. 3
3.2 Lines & Angles
Theorems
Thm. 3.2: If two sides of two adjacent acute
are perpendicular, then the angles are
complementary.
diagram …
Ch. 3
3.2 Lines & Angles
Theorems
Thm 3.3: If two lines are perpendicular, then
they intersect to form four right angles.
diagram …
Ch. 3
3.2 Lines & Angles
Wrap-Up
With partner …represent this statement in a
flow proof:
If ABC is a right triangle with hypotenuse AB
then AC 2  BC 2  AB 2
*
hint: draw the triangle and think of the Pythagorean
theorem
Ch. 3
3.2 Lines & Angles