Reason: ≈ 1+∠4 = 180 (defined as a right angle), ∠ 1+∠ 2 = 180 (known).
∴∠2=∠4.
∴EF∥AB (internal dislocation angles are equal and two straight lines are parallel).
∴∠3=∠ADE (two straight lines are parallel with equal internal angles).
∫∠3 =∠B (known),
∴∠B=∠ADE (equivalent substitution).
∴DE∥BC (same angle, two straight lines are parallel).
∴∠ AED =∠∠ ACB (two straight lines are parallel and have the same angle).
I called myself. It's hard. Hope to adopt. thank you
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