The curved surface area of a cone of slant height l and radius r is given by (1) 1/3 πr2 (2) πrl (3) π rl2 (4) 1/3 πrl.
The curved surface area of a cone is the measurement (perimeter) of the curved face.
Answer: The Curved Surface Area of a cone is πrl.
Let's see how?
Given in the question that, the radius of the cone is r and the slant height of the cone is l.
Since a cone looks like a square pyramid with a circular base and curved surface, its curved surface area, and lateral surface area are related.
The lateral surface area of a triangular face in a square pyramid is 1/ 2 a × l, where a is the altitude and l is the slant height of the square pyramid.
If we replace 'a' by '2πr' as the cone has a curved face with a circular base then we get,
⇒ 1 / 2 (2πr) × l