10. Write a program to demonstrate Trapezoidal rule.

            
        /* Program to execute trapezoidal rule*/
	#include<stdio.h>
	#include<conio.h>
	#include<math.h>
	float calc ( float );
	void main()
	{
	    float x0,xn,h,y;
	    int i,sn;
	    printf("Enter values of  x0,xn and number of sub-intervals: ");
	    scanf("%f%f%d", &x0, &xn, &sn);
	    h=(xn-x0)/sn;
	    y=calc(x0) + calc(xn);
	    for(i=1; i<sn; i++)
	        y +=2*calc(x0+i*h);
	    y=(h/2)*y;
	    printf("Value of integral is %f",y);
	    getch();
	}
	float calc(float x)
	{
	    return 1/(1+x*x);
	}