Monday, February 09, 2009
Geometry (Class 49)
Lesson Title
Proving Triangles Congruent (4)
Overview
Our opener today focuses on review multiplication and factoring skills from Algebra 1. The lesson for the day will focus on deepen student ability to prove triangles congruent. As time permits we will also prove a new, and much anticipated, theorem concerning sides and angles of isosceles triangles as well as take another look at ways to prove triangles congruent.
Textbook Sections
Vocabulary
construction
straight edge
arc
radius
center
diameter
adjacent
opposite
included
non-included
SSS
ASA
SAS
Key Attitudes
Math is about being convinced a statement is always true.
Key Ideas
A factor answers the question “How many of these are in this”?
Triangles can be constructed out of various combinations of angles and sides.
Only some combinations of angles and sides guarantee that all triangle created with this combination will be congruent-- the same size and the same shape. Other combinations only guarantee triangles which are the same shape, and some combinations guarantee nothing at all!
When multiplying two expressions, if the bases are the same the exponents need to be added.
Key Skills
I can identify key angle and side combinations which force triangles to be congruent.
I can identify and sequence the reasons which establish triangle congruence.
I can construct parallel lines.
I can construct the midpoint of a segment.
Turn-In (#48)
Txt. p.216 #12-17, 21-23 (For #23, don’t worry about doing a “paragraph” proof-- doing a 2 column is fine).
Handouts
No Handouts Posted
Assignment
Txt. p.218 #25, 26
Disclaimer- The assignment as stated in class is the official assignment. Every effort is made to keep this posting accurate, but you should refer to what was stated in class as the final word.
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