It is given that α,β,γ are the lengths of tangents from vertices of a triangle to its incircle semi perimeter of ΔABC. Consider the figure shown below.
So, S=α+β+γ And, Area of Δ‌ABC=√s(s−a)(s−b)(s−c) =√(α+β+γ)(α)(β)(γ) Also, r=