I have taken c++ but it has been about a year ago. I am taking mechanics of materials now and need to solve a bending moment problem. I am trying to get values of Sigma when a is between 0 and 20mm in 2mm increments. I have wrote a little bit of code and need to figure out if this would the correct approach? Also why is this loop infinite?
I do not have a copy of my text anymore so any help would be appreciated.

The equation I am solving for is Sigma = MC / I
Remember I need 16 values for Sigma when a is varying.

using namespace std;
int main()
    double n,M,C,I,Sigma,b,h,a,x,i;
    n = 2.66;
    C = .020;
    M = 1500;
           Sigma = (1500 * .020)/ ((1/12)*(.060)*pow(.040-2*a,3));
    return 0;