Hi, im trying to code a function that takes the integral of a given function usi

Question

Hi, im trying to code a function that takes the integral of a given function using trapezoidal rule, but I cant get the code to give the right answer.

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
int n;
char q;
float a, b;
double integrate(double a, double b, int n)       //Evaluates the Integral
{
   int i;
   float x;
   float k = (b - a) / n;
   float l = (b + a) / 2;
   float v;
   for (i = 1; i < n; i++) {
       x = b + k * i;
       v = l + f(x);
   }
   return l*k;
}

double f(double x)
{
   float h;
   h = x;
(x)= sin(h) + ((h*h) / 10);

}

When a is set to -2.1, b set to 1.5 and N set to 15, the given answer is -0.07200, however the answer should be -0.14816

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
int n;
char q;
float a, b;
double integrate(double a, double b, int n)       //Evaluates the Integral
{
   int i;
   float x;
   float k = (b - a) / n;
   float l = (b + a) / 2;
   float v;
   for (i = 1; i < n; i++) {
       x = b + k * i;
       v = l + f(x);
   }
   return l*k;
}

double f(double x)
{
   float h;
   h = x;
(x)= sin(h) + ((h*h) / 10);

}

Explanation / Answer

// C program to implement Trapezoidal rule
#include<stdio.h>
#include <math.h>

double y(double x)
{
float h;
h = x;
x= sin(h) + ((h*h) / 10);
return x;
}

//Evaluates the Integral
float integrate(double a, double b, double n)
{
// Grid spacing
float h = (b-a)/n;

// Computing sum of first and last terms
// in above formula
float s = y(a)+y(b);

// Adding middle terms in above formula
int i;
for (i = 1; i < n; i++)
s += 2*y(a+i*h);

// h/2 indicates (b-a)/2n. Multiplying h/2
// with s.
return (h/2)*s;
}

// Driver program to test above function
int main()
{
// Range of definite integral
double x0 = -2.1;
float xn = 1.5;

// Number of grids. Higher value means
// more accuracy
int n = 15;

printf("Value of integral is %6.4f ",
integrate(x0, xn, n));
return 0;
}

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