Areas
square = a2 
rectangle = ab 
parallelogram = bh 
trapezoid = h/2 (b1 + b2) 
circle = pi r 2 
ellipse = pi r1 r2 
triangle = (1/2) b h 
equilateral triangle = (1/4)
(3) a2
triangle given SAS = (1/2) a b sin C
triangle given a,b,c = ![[sqrt]](http://math2.org/math//symbols/sqrt.gif "[sqrt]")
[s(s-a)(s-b)(s-c)] when s = (a+b+c)/2 (Heron's formula)
regular polygon = (1/2) n sin(360°/n) S2
when n = # of sides and S = length from center to a corner
Volumes
cube = a3 
rectangular prism = a b c 
irregular prism = b h 
cylinder = b h = ![[pi]](http://math2.org/math//symbols/pi-l.gif "[pi]")
r2 h 
pyramid = (1/3) b h 
cone = (1/3) b h = 1/3 r2 h 
sphere = (4/3) r3
ellipsoid = (4/3) pi r1 r2 r3 
Surface Areas
cube = 6 a2
prism:
(lateral area) = perimeter(b) L
(total area) = perimeter(b) L + 2b
sphere = 4 r2
http://math2.org/math/geometry/areasvols.htm