Area of A Cone

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Cone is a geometric figure with a fixed vertex and a circular base. The curved surface area of the cone = π * r * s. Here r is the radius and s is the length of the slant side. Slant side, s = √(r2+h2). The height 'h' of the cone from the vertex of the cone and the radius 'r' of the circular base make a right angle.

Example 1: What is the curved surface area of the cone which has the base radius r of 3 cm and height 4 cm?

The base radius of the given cone is 3 cm, i.e. r = 3 cm.
The height of the cone, h = 4 cm.
The slant height of the cone, s = √(r2 + h2).
s = √(32 + 42) = √(9 + 16) = 5cm .

Area of cone = π * r *s

This makes the solution = 3.14 * 3 * 5 = 47.1 cm2

Hence, curved surface area = 47.1 cm2 approximately.

Example 2: What is the curved surface area of the cone which has the base radius r of 5 cm and height 12 cm?

The base radius of the given cone is 5 cm, i.e. r = 5 cm.
The height of the cone, h = 12 cm.
The slant height of the cone, s = √(r2 + h2).
s = √(52 + 122) = √(25 + 144) = 13 cm .

Area of cone = π * r *s

This makes the solution = 3.14 * 5 * 13 cm2 = 204.1 cm2

Hence, curved surface area = 204.1 cm2 approximately.