Circle
A = πr² C = 2πr
Rectangle
A = ℓw
Triangle
A = ½bh
Pythagorean
c² = a² + b²
Special right △
30-60-90: x, x√3, 2x
45-45-90: s, s, s√2
Rectangular solid
V = ℓwh
Cylinder
V = πr²h
Sphere
V = 4⁄3 πr³
Cone
V = 1⁄3 πr²h
Pyramid
V = 1⁄3 ℓwh
A circle has 360° (2π radians). The angles of a triangle sum to 180°.