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3. Given triangle ABC = triangle DEF, which statement is not always true?(
(1) BC = DF.
BC and DF are not corresponding sides. BC corresponds to EF and DF corresponds to AC. They would only be congruent if the triangles were isosceles or equilateral. We don't know whether they are or not.
4. In the diagram below, DE, DF and EF are midsegments of triangle ABC.
The perimeter of quadrilateral ADEF is equivalent to
(4) AB + AC.
FE = DB and DE = FC. So AD + DE + EF + FA = AD + FC + DB + FA.
Rearrange the terms: AD + DB + AF + FC = AB + AC.
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