A.Yes, it's my pencil.
B.He's ten.
C.It's under the desk.
D.Yes, it is.
如图,已知长方形ABCD的周长为20,AB=4,点E在BC上,AE⊥EF,AE=EF,求CF的长.
两个圆的面积相等,这两个圆的周长一定也相等.