Problem preview
G-CO.8 Warmup M1-043-A09-V01

Explain ASA, SAS, and SSS triangle congruence criteria from rigid-motion congruence.

Complete a missing proof statement or reason

Problem

Complete the missing statement or reason in this proof step: \(AB=DE\), \(BC=EF\), \(\angle~B=\angle~E\), so \(\triangle~ABC~\cong~\triangle~DEF\) by .

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What this problem is really about

To fill a proof blank, classify each given as a side fact or an angle fact before naming any theorem. Then check the angle’s placement relative to the known sides; only after the evidence forms a valid pattern should you write the congruence statement and the reason that supports it.

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Four variants of this problem type
Curriculum context
Course
Math I
Standard
G-CO.8
Category
Geometry
Domain
Congruence
Objective
Explain ASA, SAS, and SSS triangle congruence criteria from rigid-motion congruence.
Problem type
Complete a missing proof statement or reason