• The lateral area of a right circular cone is π r l, where r is the radius of the base and l is the slant height.
• This can be seen by unrolling the curved surface: it becomes a circular sector of radius l, whose arc has length equal to the circumference of the base, 2π r.

Lateral area = π r l

Area of the base = π r²

Total area = π r l + π r² = π r (r + l)

1. We use π ≈ 3.14 when an approximate answer is needed
2. or we leave the answer in terms of π for the exact value.