证明:设正方形AEDB和正方形ACFG的边长分别是a,b.
AN/GF=BA/BG⇒AN/b=a/(a+b)⇒AN=ab/(a+b)
AM/ED=CA/CE⇒AM/a=b/(b+a)⇒AM=ab/(a+b)
∴AN=AM