Question

如图,在正方形ABCD中,E为BC的中点,F为CD的四等分点,连结AE,AF,EF.说明三角形AEF是直角三角形

Answer 1

设AB=1,BE=1/2,CF=1/4,DF=3/4,AD=1,AE^2=AB^2+BE^2=5/4,EF^2=CE^2+CF^2=5/16,

AF^2=AD^2+DF^2=25/16,AE^2+EF^2=5/4+4/16=25/16=AF^2,根据勾股定理逆定理,∴△AEF是RT△.