1.在△ABC中,∠BAC=90°,AB=AC,點(diǎn)D在邊BC上,
,將線段DB繞點(diǎn)D順時(shí)針旋轉(zhuǎn)至DE,記旋轉(zhuǎn)角為α,連接BE,CE,以CE為斜邊在其一側(cè)作等腰直角三角形CEF,連接AF.
(1)如圖1,當(dāng)α=180°時(shí),線段AF與線段BE的數(shù)量關(guān)系為
.
(2)當(dāng)0°<α<180°時(shí),
①如圖2,(1)中線段AF與線段BE的數(shù)量關(guān)系是否仍然成立?請(qǐng)說明理由;
②如圖3,當(dāng)BC=15,且點(diǎn)B,E,F(xiàn)三點(diǎn)共線時(shí),求線段AF的長(zhǎng).