As shown in the figure, in the square ABCD, points E and f move on BC and CD respectively, but the distance ah from a to ef always keeps the same as AB, etc? Please explain the reason. (2) does the circumference of △ ECF change? Please give reasons

(1) The reasons are as follows: according to the meaning of the title, we know AB = ah, ∠ B = 90 ° and ∵ ah ⊥ EF, ∵ ahe = 90 °, ∵ AE = AE, ∵ RT △ BAE ≌ RT △ hae (HL), ∵ BAE = ∠ hae, similarly, ≌ HAF ≌ △ DAF,

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