Then BE=y-x

Through the similar (y-x)/x=x/y

y & ampsup2-x & amp； sup2-xy=0

Both sides of the equation are obtained at x & x & sup 2.

(y/x)& amp； sup2-y/x- 1=0

Y/x= (radical number 5+ 1)/2

In fact, it is x:y= golden ratio.