Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
6. Proving Triangle Congruence by ASA and AAS
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Exercise 3 Page 629

∠ RTS and ∠ UTV are vertical angles.

See solution.

Practice makes perfect

From the diagram, we know that an angle and a side are congruent in △ RST and △ TUV. Observing the diagram, we can also identify two vertical angles, ∠ RTS and ∠ UTV. By the Vertical Angles Congruence Theorem, these angles are congruent as well.

Now we have enough information to prove congruence using the ASA Congruence Theorem.

Alternative Solution

Two-Column Proof
Let's show this as a two-column proof as well.

Statement
Reason
1.
∠ S ≅ ∠ U, RS ≅ VU
1.
Given
2.
∠ RTS and ∠ UTV are vertical angles
2.
Definition of vertical angles as shown in the diagram
3.
∠ RTS ≅ ∠ UTV
3.
Vertical Angles Congruence Theorem
4.
△ RST ≅ △ VUT
4.
AAS Congruence Theorem