Area

Area Formulas

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)