It will be assumed that you are familiar with the results from Euclidean and coordinate geometry listed below.
Area of a parallelogram:
Area of a triangle:
Area of a trapezoid:
We will always assume that angles are measured in radians unless otherwise specified. If an angle is inscribed in a circle of radius and is the length of the subtended arc, then
A right angle is and the sum of the angles of a triangle is . When is four right angles in (C.113) we get
Area of a circular sector: