Using trapezoidal method to compute integral

[topgun303]

The program will compute the integral of a function f.
f(x)=exp(-x^2)

The program runs but i am getting wrong values. I am guessing i made mistake somewhere in the formula.

Answer should look like the following:

Number of subintervals: 1000000Left endpoint: 0.0Right endpoint: 100.00, answer: 0.886227

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
double f(double);


int main()
{
    double upperBound;
    double lowerBound;
    double n;
    double h;
    printf(" Enter upper and lower bound values \n");
    scanf(" %lf %lf", &upperBound, &lowerBound);
    printf(" Enter number of N values \n");
    scanf(" %lf", &n);
    //h = ((upperBound - lowerBound)/n);
    //double x=lowerBound;
    for (int i=0; i<n; i++)
    {
    //double x = lowerBound;
    double f(double x);


    //x = x + h;
    }
    printf(" The result is %lf\n", f);
    getch();
}


double f(double x)
{
   return exp(-x*x);
}

Thanks For your help.
I have also attached the file. I am using Dev c++ IDE.

[oogabooga]

This is not a function call. It's just a function declaration.

double f(double x);