Lesson 11-1: Congruent Triangles
TSW: Use the fact that congruent triangles have congruent corresponding
parts.
TSW: Determine unknown angle measures or side lengths in congruent triangles.
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When you write a congruence statement like ABC ≅ DEF , you
write the vertices so that corresponding parts are in the same order.
So, what can you can conclude from this statement?
AB≅ DE, BC≅ EF, AC ≅ DF, ∠A ≅∠D, ∠B ≅∠E, and ∠C ≅∠F.
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a.
b.
c.
d.
e.
Not possible
15cm
47°
Not possible
No. All equilateral triangles have the same angle
measures, but can have different side measures.
Therefore, the triangles may not be congruent.
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Answers on Next Slide.
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4. Yes. Congruent triangles have side lengths with the same measures, and therefore the sum of their
side lengths will be the same.
5. No. Congruent triangles have the same angle measures. Since all angles of an acute triangle are
acute angles, and since one angle of a right triangle is a right angle, the angles of the two triangles do
not have the same measures, and therefore are not congruent.
6. a. CD b. DA c. DCA d. CAD
8. 18in.
7. a. HJ b. PR c. J d. P
9. D = 39°
10. 73in.