There are two sections after cutting, so the area of one section is 5 square centimeters. And this interface is an isosceles triangle. 5= 1/2 x bottom x5 is 2 according to the area = 1/2 x bottom x height.

2 is the diameter of the circle at the bottom of the cone, so the radius is 1, so the s circle = π*r*r =π* 1* 1=π square centimeter.