# Numerical Methods: Integration of given function using Trapezoidal rule in C

Source Code:

///integration of given function using Trapezoidal rule
#include<stdio.h>
float y(float x){
return 1/(1+x*x);
}
int main(){
float x0,xn,h,s;
int i,n;
printf("Enter x0, xn, no. of subintervals: ");
scanf("%f%f%d",&x0,&xn,&n);
h = (xn-x0)/n;
s = y(x0) + y(xn);
for(i = 1; i < n; i++){
s += 2*y(x0+i*h);
}
printf("Value of integral is %6.4f\n",(h/2)*s);
return 0;
}
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### 2 Responses

1. Anonymous says:

why %6.4f ?? could you explain this please. Help would be much appreciated, because so far this is the cleanest most nice structured example of the Trapezoidal rule. I need help, because i got an exercise that is about numerical integration.

Write a C-program which carries out “Numerical Integration” according to (1). Use data
type double everywhere. “Play” with three different step sizes (b-a) by splitting up the area
under f(x) into 10, 100 and 1000 trapezoids and compare the results.
Preferably, use a function for the calculation of (1) and call it from main( ).

So yeah ;/