1. Intro to Geometry Day 4
Congruence / Triangles
Warm up:
What do these all How do these c. is the only
have in common? differ from Orks? ork
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2. a.
2

3. b.
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4. A good definition...
• is precise. Avoids vague words like some, small, or rounded.
• places in object in a category, and describes how it differs
from other things in the category.
Example: A hexagon is a polygon with 6 sides.
category how it differs
• is reversible. For example, we could say
A polygon with 6 sides is a hexagon
The reverse is called the CONVERSE of the statement.
In a good definition, the converse will also be true.
How could it not be true?
4

5. Work with your partner/group to write a good definition for
each geometric term in the handout.
You are finished when you...
AGREE on the definition
and
WRITE it down.
Note: the hashmarks on a side indicate that the sides are
congruent. A
These marks mean that
C
T
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6. right triangle:
6

7. 7

8. 8

9. 9

10. 10

11. 11

12. median:
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13. median:
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14. Summary
None ≅ Two ≅ Three ≅
Scalene Isosceles Equilateral
Sides
All Acute One Obtuse One Right
Angles Acute Obtuse Right
Any triangle is classified with BOTH. (Which pairs are
impossible?) Let's Draw A....
Isoceles Right Scalene Obtuse
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15. Attachments
Lesson 4­1 adapted.pdf
Practice 4­1.pdf
Activity 9­10 Defining Triangles.pdf