# Thread: Using trapezoidal method to compute integral

1. ## Using trapezoidal method to compute integral

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

Code:
```#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);
}```
`double f(double x);`