SSS congruence rule.
Solution:
Given ΔABC and ΔDEF are congruent.
To prove that on which rule they are congruence.
In triangle ABC,
AB = 2.5 cm, BC = 1.8 cm, CA = 1.8 cm
In triangle DEF,
DE = 2.5 cm, EF = 1.8 cm, FD = 1.8 cm
Consider ΔABC and ΔDEF,
AB = DE (Side)
BC = EF (Side)
CA = FD (Side)
∴ ΔABC ≅ ΔDEF (by SSS congruence rule)
Hence, the given triangles are congruent by SSS congruence rule.
