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SSS (Side-Side-Side) Postulate

If the three sides of a triangle are congruent to the three sides of another triangle, then the two triangles are congruent.

In the figure, A B ¯ D E ¯ , B C ¯ E F ¯ and A C ¯ D F ¯ .

Therefore, by the SSS postulate, Δ A B C Δ D E F .