2. The diagonal of a square is $2 \sqrt{2}$, and the two diagonals coincide with the coordinate axes. Then the distance from the origin to one side of the square is:
(A) 1;
(B) $\backslash 2$;
(C) 2 ;
(D) $2 \sqrt{2}$.
Answer: (A).
As shown in the figure, $\triangle O \mathrm{AD}$ is an isosceles right triangle, with the legs being $\sqrt{2}$, and the hypotenuse being $2.0$. $\mathrm{O}$ is the distance from $\mathrm{O}$ to $\mathrm{AD}$, then $\mathrm{OM}$ $=1$.