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Question
Math
Posted 10 months ago

Below are ABC\triangle A B C and DEF\triangle D E F. We assume that AB=DEA B=D E, mA=mDm \angle A=m \angle D, and mB=mEm \angle B=m \angle E.

Here is a rough outline of a proof that ABCDEF\triangle A B C \cong \triangle D E F :
1. We can map ABC\triangle A B C using a sequence of rigid transformations so that A=DA^{\prime}=D and B=EB^{\prime}=E. Show drawing.
2. If CC^{\prime} and FF are on the same side of DEundefined\overleftrightarrow{D E}, then C=FC^{\prime}=F. Show drawing.
3. If CC^{\prime} and FF are on opposite sides of DEundefined\overleftrightarrow{D E}, then we reflect ABC\triangle A^{\prime} B^{\prime} C^{\prime} across DE\stackrel{\longleftrightarrow}{D E} and then C=F,A=DC^{\prime \prime}=F, A^{\prime \prime}=D and B=EB^{\prime \prime}=E. Show drawing.

Answer two questions about this proof.
1) How did we show that the triangles were congruent?

Choose 1 answer:
(A) We mapped one figure onto the other using rigid transformations.
(B) We mapped one figure onto the other using any kind of transformations.
(C) We showed that all corresponding sides had equal lengths and all corresponding angles had equal measures.
2) What triangles did we show are congruent?

Choose 1 answer:
(A) Triangles where 2 pairs of corresponding angles have the same measure, and the included corresponding sides have the same length
(B) Triangles where 2 pairs of corresponding angles have the same measure
(C) All triangles
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Answer from Sia
Posted 10 months ago
Solution by Steps
step 2
Rigid transformations include translations, rotations, and reflections, which preserve the size and shape of geometric figures
step 3
By mapping AA to DD and BB to EE, and ensuring that CC' and FF are either coincident or can be made coincident through reflection, we establish congruence of the triangles
step 4
The congruence of ABC\triangle ABC and DEF\triangle DEF is shown by the fact that they can be superimposed through these transformations
1 Answer
A
Key Concept
Rigid transformations to prove congruence
Explanation
Rigid transformations preserve the size and shape of figures, so mapping one triangle onto another using these transformations proves congruence.
step 1
The triangles we showed to be congruent have two pairs of corresponding angles with the same measure and the included corresponding sides of the same length
step 2
This is based on the given information that AB=DEAB=DE, mA=mDm\angle A=m\angle D, and mB=mEm\angle B=m\angle E
step 3
These conditions satisfy the Angle-Side-Angle (ASA) congruence criterion for triangles
2 Answer
A
Key Concept
ASA Congruence Criterion
Explanation
Two triangles are congruent if two angles and the included side of one triangle are equal to two angles and the included side of the other triangle.

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