Explain, why


From the given figure, it is clear:


ABC = FED (i)


Also,


BAC = EFD (ii)


Therefore,


The two angles of ABC are equal to the two respective angles of FED


Also,


We know that:


Sum of interior angles of a triangle is equal to 180o


Hence,


The third angle of both the triangles will also be equal


Thus,


BCA = EDF (iii)


Therefore,


From (i), (ii) and (iii)


FED


By AAA congruence criterion


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