## It is not possible to prove one pair of triangles congruent and then use their congruent corresponding parts to prove another pair congruent

Question

It is not possible to prove one pair of triangles congruent and then use their congruent corresponding parts to prove another pair congruent. True or false

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2 weeks 2021-10-14T01:39:32+00:00 2 Answers 0

true

The wording does not quite mean anything,

but what I think was meant to ask is

“if we use some parts of two triangles to prove they are congruent,

can we then use that to prove that

a pair of corresponding parts not used before are congruent?”

Yes, of course,

Corresponding Parts of Congruent Triangles are Congruent,

which teachers usually abbreviate as CPCTC.

For example, if we find that

side AB is congruent with side DE,

side BC is congruent with side EF, and

angle ABC is congruent with angle DEF,

we can prove that triangles ABC and DEF are congruent

by Side-Angle-Side (SAS) congruence.

We then, by CPCTC, can conclude that other pairs of corresponding parts are congruent:

side AB is congruent with side DE,

angle BCA is congruent with angle EFD, and

angle CAB is congruent with angle FDE.

It was possible (by CPCTC) to prove those last 3 congruence statements,

after proving the triangles congruent.