TETRA(Sphere in a tetrahedron) spoj solution

HII GUYS  this is the Geometry based problem.......
Here are some important points regarding tetrahedron.
1.there are total 4 faces of a tetrahedron
2.how to find area of one face so u know that this is a triangle
u can find its area by Hero's formula
Hero's formula is ::::
let sides of a triangle are a,b,c
then perimeter(s)  is equal to 2*s=(a+b+c)
area of triangle =sqrt(s*(s-a)*(s-b)*(s-c))

3.BY this u can find area of every triangle 
then let total area of all faces is equal to T=area1+area2+area3+area4


4.how to find volume for this i m giving u a link there u can find out
that how to calculate volume in terms of sides
link::http://en.wikipedia.org/wiki/Tetrahedron

5.after calculating volume u can use formula for radius of insphere is
=V*3/T
where V is volume
and T is surface area as i mentioned above..........

6.for volume u can also use this formula
       vol=sqrt(4*u*u*v*v*w*w- u*u*(v*v+w*w - U*U)*(v*v+w*w-U*U) - v*v*(w*w+u*u - V*V)*(w*w+u*u-V*V) - w*w*(u*u + v*v - W*W)*(u*u+v*v-W*W) + (v*v +w*w - U*U)*(w*w+u*u- V*V)*(u*u+v*v - W*W))/12
where u,v,w,W,V,U are sides of tetrahedron.....




if still u have u can see my AC SOLUTION>>>>>>>>>

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#include<bits/stdc++.h> using namespace std; double area(double ,double ,double ); int main() { int t; scanf("%d",&t); while(t--) { double u,v,w,U,V,W; scanf("%lf %lf %lf %lf %lf %lf",&u,&v,&w,&W,&V,&U); double vol; double S=0; S+=area(u,V,w); S+=area(W,u,v); S+=area(W,V,U); S+=area(U,v,w); vol=sqrt(4*u*u*v*v*w*w- u*u*(v*v+w*w - U*U)*(v*v+w*w-U*U) - v*v*(w*w+u*u - V*V)*(w*w+u*u-V*V) - w*w*(u*u + v*v - W*W)*(u*u+v*v-W*W) + (v*v +w*w - U*U)*(w*w+u*u- V*V)*(u*u+v*v - W*W))/12; printf("%.4lf\n",vol*3.0/S); } return 0; } double area(double a1,double a2,double a3) { double s=(a1+a2+a3)/2.0; return sqrt(s*(s-a1)*(s-a2)*(s-a3)); }