C/C++ :: Why Won't Functions Process New Values

I was given an assignment where I have to input two points (four integers) on a Cartesian plane from a file and then process it using functions. My professor is very particular so the comments are a bit excessive, but here's what I have.

double radiusFn(double, double, double, double);//4 double values, one for each point. All points are needed for the calculation of distance in this function.
double diameterFn(double);//Only uses one double value - the radius. Both functions below use the same value.
double circumferenceFn(double);
double areaFn(double);
int main() {

[code].....

The file reads:

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