Finding AreaSquareA = a^{2}, in which a is one of the sides. RectangleA = ab, in which a is the base and b is the length. ParallelogramA = bh, in which b is the base and h is the height. CircleA = πr^{2}, in which π is 3.1416 and r is the radius. EllipseA = πr_{1}r_{2}, in which π is 3.1416, r_{1} is the longer radius, and r_{2} is the shorter radius. TrapezoidA = (h[b_{1} + b_{2}])/2, in which h is the height, b_{1} is the longer parallel side, and b_{2} is the shorter parallel side. TriangleGiven base and height: A = (1/2)bh, in which b is the base and h is the height. Given side, angle, side (SAS): (1/2) ab x sinθ, in which a is one side, b is another side, and θ is the known angle. Given three sides: when s = (a + b + c)/2 (Heron's formula), in which a, b, and c represent the three sides.
