7. Using Congruent Triangles
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What can you conclude about BC in â–³ ABC and â–³ DBC?
See solution.
If we can show that △ ABD ≅ △ CBD , then we can prove that ∠A ≅ ∠C. Since the two triangles share BD as a side, we can by the Reflexive Property of Congruence say that these sides are congruent. Let's mark this in our diagram.
Since the three sides of △ ABD are congruent to corresponding sides of △ CBD, we can by the SSS Congruence Theorem prove that △ ABD ≅ △ CBD. Now, we can also say that ∠A ≅ ∠C since these are corresponding angles.