The Columbia Encyclopedia, Sixth Edition. 2001-07.
Formulas for Various Areas (table)
Plane Figures
Area1
triangle
ab/2
parallelogram
ab
rectangle
ab
square
s2
circle
r2
Solids
Total Surface Area1
right circular cylinder
2r(r + a)
right circular cone
r(r + l)
sphere
4r2
1 The abbreviations used are: b = base (length of any side of a plane figure); a = altitude (perpendicular distance from the farthest point of the figure to the extended base); s = side; r = radius (of the base circle in the case of the cylinder or cone); l = slant height (distance from vertex to base of a cone measured on its surface).
r2
