If a line moves in the space so that one end is kept fixed (point A) while the other end of the line is moved around the closed curve[color=#0000ff], the surface formed is called closed conic surface[/color]. The point A is called [color=#0000ff]the apex[/color]. The area of the closed curve is called [color=#0000ff]the base of the cone[/color].[br][br]If the [color=#0000ff]base[/color] of the cone is a circle, it is called a [color=#0000ff]circular cone[/color]. If the [color=#0000ff]base is a polygon[/color], it is called a [color=#0000ff]pyramid[/color]. [br][br]If the base of a cone is a polygon and the height from the apex is in the midpoint of the polygon, it is called [color=#0000ff]a regular cone[/color]. A circular cone is called [color=#0000ff]a right circular cone[/color] if the perpendicular height from the apex comes to the midpoint of the base.[br][br]Volume of a cone:[br][br]  [math]\large \textcolor{blue}{V=\frac{1}{3}Ah},[/math][br][br]where [i]A[/i] is the area of the base and [i]h[/i] is the perpendicular height of the cone.[br][br]