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<AFD= <CEF if AB _l_ AC, AB=BC, AD=//DB, DE=_I_DF, BE _|_ EC

Source: China Northern MO 2022 p1 CNMO

October 28, 2022
geometryisosceles right triangleequal angles

Problem Statement

As shown in the figure, given △ABC\vartriangle ABC with AB⊥ACAB \perp AC, AB=BCAB=BC, DD is the midpoint of the side ABAB, DF⊥DEDF\perp DE, DE=DFDE=DF and BE⊥ECBE \perp EC. Prove that ∠AFD=∠CEF\angle AFD= \angle CEF. https://cdn.artofproblemsolving.com/attachments/9/2/f16a8c8c463874f3ccb333d91cdef913c34189.png
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