This calculator uses the formula
r = sqrt [ (s - a)(s - b)(s - c) / s ] where s = (a + b + c) / 2
How to use the calculator
Enter the sides a, b and c of the triangle as positive real numbers and press "enter". The output is the radius of the inscribed circle. If one of the sides of the triangle is negative or the sum of any two sides is smaller that the third one (i.e the triangle does not exist), the anser " not valid " is displayed.
More Online Geometry Calculators and Solvers.