According to the meaning: BE=CE=2X, CF=X, DF=3X,
In rtδABE, AE 2 = AB 2+BE 2 = 20x 2,
In rt δ cef, ef 2 = ce 2+cf 2 = 5x 2,
In rt δ ADF, af 2 = ad 2+df 2 = 25x 2,
∴AE^2+EF^2=AF^2，
∴∠AEF=90 .
Mathematics is a kind of wisdom, which contains wonderful, concrete and abstract thinking, inheritance and transcendence of numbers an