In the triangle ABC, the angle ACB is 90 degrees, CD is perpendicular to point D, point E is on point AC, CE = BC, make a vertical line of AC through point E, and intersect the extension line of CD at point F Prove that angle a is equal to angle F

It's very simple to prove that ∠ = ∠ f is generally based on the congruent △ principle, that is to prove the congruence of △ ACB and △ FEC: ∵ CD ⊥ ab ∪ DCB + ∠ B = 90 °

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