The emphasis on a “sequence of rigid motions” (which comes up often in exams and curricular materials) may be because the curriculum emphasizes reflection, rotation, and translation as the basic rigid motions while mostly ignoring glide reflections (composition of translation and reflection).

]]>However, the additional information regarding the mapping of point A to D and point C to F via rigid motion guarantees that segment AC is congruent to segment DF. Together with the congruent angles, this allows us to conclude the triangles are congruent.

]]>This is definitely not what was meant. This language is used consistently (in prior exams and in curricular materials) to refer to the original figure and the final image. I’m sorry to say your charity is in vain.

]]>This would still be a poor question (wrapping a simple question about the inadmissibility of SSA and AAA and mere SA as congruence tests in layers of obfuscation), but at least one that is mathematically correct.

In fact, I can read this meaning into what they wrote as the question; of course, the wording used (“a sequence of rigid motions…”) is not clear about whether the tested conditions are during the sequence or after the entire sequence was applied.

But perhaps therein lies the problem, and the official excuse is less inaccurate than you imagined.