The picture shows an archway of a scenic spot in Wuwei Middle School, which is a part of ⊙ O. It is known that the ground width of the archway is CD=2m and the maximum height is EM=3m. Find it.
Solution: Connect OC. Let the radius of ⊙O be xm,
∵EM⊥CD，
∴CM= 12CD= 1m.
At Rt△OCM, OM2+CM2=OC2.
Get (3-x) 2+ 1 = x2.
Solution: x = 53.
A: The ⊙O radius of the arch is 53 meters.