Download Congruent Triangles - TEACHER

Congruent Triangles - TEACHER
(1) Draw a triangle with one side 2 inches long.
How does your drawing compare with the drawings next to you?
smaller, thinner, wider, more obtuse, FEW should answer Congruent.
(2) Draw a triangle with a side 3 & another side 3 inches.
How does your drawing compare with the person next to you?
smaller, thinner, wider, more obtuse, FEW should answer Congruent.
(3) Draw a triangle with sides 3, 4, and 5 inches.
How does your drawing compare with the drawings next to you?
All students should answer Congruent.
“We know that if a pair of sides “S”, another pair of sides “S”,
and yet another pair of sides “S” are congruent, then we will have
congruent triangles.” This is called the :___SSS_____ postulate.
“S” stands for a _pair____ of _Sides____ , one in each triangle.
“A” stands for a __pair___ of _Angles____ , one in each triangle.
**********************************************************
(4) Draw a triangle with sides 3 and 4 inches. Make one of the angles be 90
degrees. How does your drawing compare with the drawings next to you?
smaller, thinner, wider, more obtuse, FEW should answer Congruent.
(5) Draw a triangle with sides 3 and 4 inches. Make the included angle
(between) 90 degrees. How does it compare to the drawings next to you?
______ All students should answer Congruent. ___________________
“We know that if a pair of sides “S”, another pair of sides “S”, and the
included angles “A” are congruent, then we always have congruent
triangles.” This is called the __SAS______ postulate.
___________________________________________
Congruent Triangles Postulates
2004 @www.beaconlearningcenter.com
4/26/2004
(6) Done without drawing. “If a pair of __angles______, another pair of
___ angles__, and the ___sides______ (between) angles are
congruent, we have congruent triangles.” This is called: ASA .
(7) “If a pair of angles “A” , another pair of __ angles_, and the NEXT pair
of sides “S” are congruent, then we always have congruent triangles.”
This is called the AAS postulate.
(8) Back to the paper and rulers. Draw a triangle with a measure of 30
degrees, 60 degrees, and 90degreees. How does your drawing compare with
the drawings next to you?__Similar, but not necessarily congruent.___
Teacher reads story.
AAA doesn’t work as a three lettered postulate to prove triangles congruent.
Summarize the story of the gym and the classroom.:___________________
_______________See students work________________________________
_____________________________________________________________
As practice look at these two situations:
Figure B
Figure C
Any line with a single tick mark, is congruent to all other lines with a single
tick mark. Double or triple tickets marks work in the same way, but in no
means tells you which line is bigger.
Since we notice pair of sides (on the vertical lines) ___S___
And we notice the next angle (both rights) _______A_____
And we notice the next pair of sides __________S_______
We can say that these two triangles are congruent by the _SAS__ postulate.
HINT: Two triangles can still be proven congruent if you move clock wise
around the first triangle and counter clockwise around the second triangle.
NO SKIPPING MORE THAN ONE ANGLE OR ONE SIDE AT A TIME.
Congruent Triangles Postulates
2004 @www.beaconlearningcenter.com
4/26/2004
Below each pair write SAS, SSS, ASA, AAS, or Not Congruent.
Not Congruent
SSS
AAS
SAS
Not Congruent
Not Congruent
SAS
ASA
ASA
Congruent Triangles Postulates
SAS
2004 @www.beaconlearningcenter.com
4/26/2004
In each pair, draw in additional information, so that the postulate below is used to prove congruency.
SAS
SSS
SAS
AAS
SSS
ASA
ASA
SAS
ASA
Congruent Triangles Postulates
SSS
2004 @www.beaconlearningcenter.com
4/26/2004