Let DX=x and the side length of a square be a, then ax = (a 2+x 2) (1/2) (that is, the square of a plus the sum of the squares of x and then open the root sign), and ay = (a 4/(x 2)+a 2) (65438+).

The following contents are used in high school knowledge: A2+B2 > = 2ab (ab > 0)

ax=(a^2+x^2)^( 1/2)>； (2ax) (1/2) (here, because A is not equal to X, it is greater than the symbol)

ay=(a^4/(x^2)+a^2)^( 1/2)>； (2a^3/x)^( 1/2)

AX+AY & gt； = 2 (AX * AY) (1/2) (that is, 2 times the root number AX times AY)

= 2 * (2a 2) (1/2) = 2 times the root number 2 * a.

And AC = (a 2+a 2) (1/2) = root number 2 * a.

So AX+AY & gt；; 2AC .

I'm really sorry, because this place is not easy to represent mathematical symbols, so it may seem a bit troublesome! -High school math teacher.