• The lateral area of a pyramid is the sum of the areas of its lateral faces.
• The total area is the lateral area plus the area of the base.
• In a regular pyramid the lateral faces are congruent triangles.
• The height of each triangle is the slant height l, and its base is one side of the base polygon.
• If the perimeter of the base is P, then:

Lateral area = ½ × P × l

Total area = ½ × P × l + area of the base

1. If the base is a square of side a
2. then P = 4a
3. and the rule for the lateral area becomes ½ × 4a × l = 2a l.