Instruction

1

A round cone is the body obtained by rotating a triangle around one of its legs. Direct, outbound from the vertex

**of the cone**and intersecting the base, called forming. If all the generators are equal, then the cone is straight. At the base of a circular**cone**is the circle. The perpendicular on the base from the top, is the height**of the cone**. Have a round straight**cone**height coincides with its axis. The axis is the line connecting the vertex with the centre of the base. If horizontal clipping plane of a circular**cone**parallel to the base, its upper base is a circle.2

Because the clause is not specified what kind of cone is given in this case, we can conclude that this is a straight circular truncated cone, horizontal section which is parallel to the base. Its axial cross-section, i.e. a vertical plane which passes through the axis of the circular truncated

**cone**, is ravnovesnoi trapeze. All of the axial**cross section**of a round straight**cone**are equal. Therefore, in order to find*the area of the*axial**cross-section**, it is required to find*the area*of a trapezoid, bases of which are the diameters of the bases of the truncated**cone**and the side of his form. The height of the truncated**cone**is both the height of the trapezoid.3

Area of a trapezoid is given by:S = ½(a+b) h, where S is

*the area*of the trapezoid;a is the value of the lower bases of the trapezoid;b – the value of its upper base;h = height of the trapezoid.4

Because the condition is not specified, what values this can be considered that the diameters of the two bases and the height of the truncated

**cone**are known: AD = d1 – the diameter of the lower base of the truncated**cone**;BC = d2 is the diameter of its upper base; EH = h1 – the height**of the cone**.Thus,*the area of the*axial**cross-section**of the truncated**cone**is determined by: S1 = ½ (d1+d2) h1