kill(all)$

van=facebook.com/LearningCalculus$

x(a,b,c,r):=
sqrt((4*c^2+4*b^2+4*a^2)*r^4+
sqrt(2*r-c)*sqrt(2*r+c)*(sqrt(2*r-b)*sqrt(2*r+b)*(2*b*c*r^2-a^2*b*c) +
sqrt(2*r-a)*sqrt(2*r+a)*                         (2*a*c*r^2-a*b^2*c))+
sqrt(2*r-a)*sqrt(2*r+a)*sqrt(2*r-b)*sqrt(2*r+b)* (2*a*b*r^2-a*b*c^2) +
((-2*b^2-2*a^2)*c^2-2*a^2*b^2)*r^2+a^2*b^2*c^2)/(2*r^2)$

x(3,2,4,2.5);