; Some more fun formulas. These are very similar to Heron's formula ; for the area of a triangle (see "heron.in"). a, b, and c are the ; lengths of the sides of the triangle. s=(a+b+c)/2 ; semiperimeter ; radius of a circle inscribed in a triangle, called an incircle: inradius=(s*(s-a)*(s-b)*(s-c))^.5/s eliminate s simplify ; The following is the equation for the radius of a circle circumscribing ; a triangle, called a circumcircle, which is a circle that passes through ; all the vertices of a polygon. radius=a*b*c/(4*(s*(s-a)*(s-b)*(s-c))^.5) eliminate s simplify