The radius of the base of a cone is 5 cm and its height is 12 cm. Its curved surface area is
Given: The height of the cone is 12 cm.
The radius of the cone is 5 cm.
Curved surface area of a cone is : πrl (here r and l are radius and slant height respectively)
l = √(r2 + h2)
∴ πrl = πr√(r2 + h2)
Let S be the CSA of the cone.
∴ S = πr√(r2 + h2)
⇒ S = π × (5) × √((5)2 + (12)2)
⇒ S = π × (5) × √(25 + 144) = π × (5) × √(169)
⇒ S = π × (5) × 13 = 65π
∴ S = 65π cm2
That is CSA of the cone is 65π cm2