Let me help you! Because triangle ADE can coincide with ABF, triangle AFB is all equal to triangle ADE, that is, angle EAD= angle BAF (the corresponding angles in congruent triangles are equal), that is, AF=AE (the corresponding sides in congruent triangles are equal). Because the angle BAE = = is 90 (the inner angle of the square is 90), it should be angle BAE = angle BAE+ angle EAD (known), so angle BAE = angle FAE= angle BAF+ angle BAE.

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