![]() We already know that cones constitute the right-angled triangle. Where r is the radius of the base and l is its slant height. ![]() So, the curved surface area = 1/2 *l* 2πr = πrl or simply The circumference of the base = 2πr, where r is the base of the radius of the base. = 1/2 l (b 1 + b 2+ b 3 + …) = 1/2 × l× (length of the whole curved boundary)Īlso, the entire curved portion makes the perimeter of the base of cones. So, the sum of the areas of many such triangles makes up the area of the sector (fig c). Now, the area of each triangle = 1/2×base of triangle×l. Furthermore, if this shape is cut into small pieces along the lines marked in the figure, you can see that the pieces look like a triangle whose height is the slant height, l. And, when you bring the sides marked P and Q together, you can see the curved portion of the shape forms a circle. ![]() If you cut a paper cone straight along its side and open it, you can see the shape of paper that forms the surface of the cone. While studying cones, we generally consider a right circular cone. Oblique Cone: In this type, the axis is non-perpendicular to the base. Right Circular Cone: In this type, the axis makes a right angle from the base. ![]() And, the distance from the vertex to a point on the base is the slant height. The shortest distance between the vertex and the base is called height. It is a three-dimensional figure and has a circular base that tapers to a point called a vertex, apex or top. In geometry, the word cone refers to a pyramid-like structure with a circle-shaped base. ![]()
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