# Calculate the area of an irregular cyclic convex polygon

I want to write a program in C++ to calculate the area of irregular cyclic convex polygons. However, the inputs are in the form corner point angles. I am just not sure what the inputs mean and what formula to use. Here is the question; I just need an explanation of what the input means and what equation to use to calculate the area.

• @NormalHuman yah but i am not familiar with the subject area do you know what it should be? – Fahad Albalawi Oct 24 '15 at 4:32

Let the radius be $r$.
Inputs are $a_i$; where $i = 1, …, n$. Of course, all input should observe the rule $0^0 \le a_i \le 360^0$.
A simple sorting and re-ordering is necessary to ensure that $a_i \lt a_j$ if $i \lt j$.
For an $a_i$, there is a corresponding con-cyclic point whose co-ordinates are $(r \cdot \cos (a_i), r \cdot \sin (a_i))$.