Problem
Two triangles, in which a pair of corresponding sides and angles at both ends of them are respectively equal, are congruent.
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Solution
Now, if we put $B$ on top of E, $C$ on top of $F$, and $A$ on the same side of $EF$ as $D$, then
$$∠B=∠E.$$
Thus, $BA$ overlaps $ED$.
Since $∠C=∠F$, $CA$ overlaps $FD$.
Therefore, $A$ overlaps $D$.
$$∴ \ △ABC≡△DEF.$$
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Reference
Teiichiro Sasabe (1976) The Encyclopedia of Geometry (2nd edition), Seikyo-Shinsha, p.9