section 43 congruent triangles - rocori high school · section 43 congruent triangles ... each...
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Section 43 Congruent Triangles
Triangles that are the same size and shape are congruent triangles.
Each triangle has three angles and three sides.
If all six of the corresponding parts of two triangles are congruent, then the triangles are congruent.
Ex:
If ABC is congruent to EFG, the vertices of the two triangles correspond in the same order as the letters naming the triangles.
Ex:
The correspondence of vertices can be used to name the corresponding congruent sides and angles of the two triangles.
Ex:
The corresponding sides and angles can be determined from any congruence statement by following the order of the letters.
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CPCTC stands for Corresponding Parts of Congruent Triangles are Congruent.
"If and only if" is used to show that both the conditional and its converse are true.
Ex 1 Identify the congruent triangles in each figure.a.
b.
c.
d.
Note: This is a parallelogram since opposite sides are parallel. Also, in a parallelogram, opposite angles are congruent.
** We will use alternate interior angles a lot in this chapter.
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Ex 2 Name the congruent angles and sides for each pair of congruent triangles.
a.
b.
Like congruence of segments and angles, congruence of triangles is reflexive, symmetric, and transitive.
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In the figures below, ABC is congruent to DEF.
If you slide DEF up and to the right, DEF is still congruent to ABC.
You can slide it anywhere and it will still be congruent (same size and shape).
The congruency does not change whether you turn DEF or flip DEF.
ABC is still congruent to DEF.
SLIDE = TRANSLATION
TURN = ROTATION FLIP = REFLECTION OR MIRROR IMAGE
If you slide, flip, or turn a triangle, the size and shape do not change.
These three transformations are called congruence transformations.
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Ex 3
a. Verify that
b. Name the congruence transformation for RST and R'S'T'.
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Ex 4 Describe the congruence transformation between the two triangles as a slide, a flip, or a turn. Then name the congruent triangles.a.
b.
c.
Assign Pgs. 195 198 # 3 5, 9 16, 20, 23 32, 38 44
Pg. 198 Quiz 1 # 1 5