Gaussian Quadrature

/* This program finds integral by gaussian quadrature*/

#include<stdio.h>
#include<math.h>

float g(float d)
{
  float f;
  p=1+d;
  return(p);
 }

void main()
{
  FILE *fp1;
  int  n,i,m;
  float u[100],w[50],sum,sum1,a,b,p1;
  fp1=fopen(“abc.dat”,”r”);
  printf(“type the number of points”);
  scanf(“%d ”, &n);
  printf(“type the lower limit a and upper limit b”);
  scanf(“%f%f ”, &a,&b);
  m=n/2;
  for(i=0; i<=n; i++)
  {
   fscanf(fp1,”%f%f”,&u[i],&w[i]);
   u[i+m] =- u[i];
   w[i+m] = w[i];
   printf(“u[i]=%f, w[i]=%f \n”,u[i],w[i]);
   }
   sum = 0;
   for(i=0; i<=n; i++)
   {
    p1= g((b-a)/2*u[i]+ (b+a)/2);
    sum = sum + w[i]*p1;
    }
    sum = sum *(b-a)/2;
    printf(“required integral = %f\n”, sum1);
    fclose(fp1);
    getch();
    }



  type the number of points n
  6
  type the lower limit a and upper limit b
0 1
u[i] = 0.236819 ,   w[i] = 0.467914
u[i] = 0.661209 ,   w[i] = 0.360762
u[i] = 0.932469,    w[i] = 0.171324
required integral = 1.500000