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Triangle & Geometric Congruence. Mr. Robinson Geometry Fall 2011. Essential Question:. How do you identify corresponding parts of congruent triangles?. The order of the ________ indicates the corresponding parts!. Δ ABC Δ XYZ. Corresponding Parts.
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Triangle & Geometric Congruence Mr. Robinson Geometry Fall 2011
Essential Question: How do you identify corresponding parts of congruent triangles?
The order of the ________ indicates the corresponding parts! ΔABC ΔXYZ Corresponding Parts If two figures are congruent, there is a correspondence between their angles and sides such that corresponding angles and corresponding sides are congruent. The parts of congruent triangles that “match” are called__________________. corresponding parts vertices
Congruent Triangles FE DE FD AC BC AB F E D In the figure, ΔABC ΔFDE. A vertices As in a mapping, the order of the _______ indicates the corresponding parts. C B Congruent Sides Congruent Angles A F B D C E These relationships help define the congruent triangles.
Congruent Triangles corresponding parts If the _________________ of two triangles are congruent, then the two triangles are congruent. congruent If two triangles are _________, then the corresponding parts of the two triangles are congruent.
Writing a Congruence Statement D C A B F E
Congruent Triangles S Z 50° 40° R (2n + 10)° 90° Y X T ΔRST ΔXYZ. Find the value of n. ΔRST ΔXYZ identify the corresponding parts corresponding parts are congruent S Y subtract 10 from both sides 50= 2n + 10 40= 2n divide both sides by 2 20= n
3rd Angles Theorem • If two ’s of one triangle are to two ’s of another triangle, then the third ’s are also .
Example: find x ) ) 22o )) 87o )) (4x+15)o
Example: Continued 22+87+4x+15=180 4x+15=71 4x=56 x=14
Properties of Congruent Triangles(Theorem 4.4) 1. Reflexive: 2. Symmetric: 3.Transitive:
Congruence and Correspondence • When 2 figures are congruent there is a correspondence between their angles and sides such that corresponding angles are congruent and corresponding sides are congruent.
Ex: ABCD is to HGFE.Find x and y. F E 9cm B A (5y-12)o 91o 86o H G 113o 4x-3cm D C 4x-3=9 5y-12=113 4x=12 5y=125 x=3 y=25
Assignment • P 206 – 209: 10 – 22, 22 – 29,