List of geometry rules

We are building a geometry app where the user can calculate the remaining values in geometric shapes in which only a limited number of values are known. The shapes inlcude: - Triangles - Right-angled triangle - Circle - Trapezium For each of these shapes, we need a list of rules that apply to the calculation of legnths, angles, and areas. By rules we mean a list of limitations to such calculations, like - The sum of all angles in a triangle can never exceed 180 degrees - The radius of a circle is always equal to (2 x Pi)/Circumference What do we need this for? The app will produce an error message if the user enters two or more conflicting values.