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(pi = = 3.141592...)

Area Formulas

Note: "ab" means "a" multiplied by "b". "a²" means "a squared", which is the same as "a" times "a".

Be careful!! Units count. Use the same units for all measurements. Examples

square = a ²
rectangle = ab
parallelogram = bh
trapezoid = h/2 (b₁ + b₂)
circle = pi r ²
ellipse = pi r₁ r₂  

triangle =

one half times the base length times the height of the triangle

  

equilateral triangle =

 
triangle given SAS (two sides and the opposite angle)
= (1/2) a b sin C
triangle given a,b,c = [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 

Volume Formulas

Note: "ab" means "a" multiplied by "b". "a²" means "a squared", which is the same as "a" times "a". "b³" means "b cubed", which is the same as "b" times "b" times "b".

cube = a ³
rectangular prism = a b c
irregular prism = b h
cylinder = b h = pi r ² h
pyramid = (1/3) b h
cone = (1/3) b h = 1/3 pi r ² h
sphere = (4/3) pi r ³
ellipsoid = (4/3) pi r₁ r₂ r₃