# C++ Program to evaluate an Definite Integral by Trapezoidal Rule

```#include  //Header file for cin & cout
#include  //Header file for mathematical operartions
using namespace std;  //calling the standard directory

//Taking a function f(x)
float f(float(x))
{
return (pow(x,3)+pow(x,2)-(4*x)-5);
}

//Taking diffrentiation of f(x) i.e. g(x)
float g(float(x))
{
return (3*pow(x,2)+2*x-4);
}

//Taking double diffrentiation of f(x) i.e. h(x)
float h(float(x))
{
return (6*x+4);
}

int main()  //Main Program
{
long double a,b,d,i,n,I=0,J=0,A,K=0,E=0;
cout<<" Given f(x)= x^3 + 2x^2 - 4x - 5 "<>a;
cout<<"Enter Upper Limit "<>b;
cout<<"Enter the number of intervals : "<>n;
d=(b-a)/n;

//Steps of solving by Trapezoidal Rule
for(i=0;i<=n;i++)
{
I=I+f(a+(i*d));
}

for(i=1;i
/*OUTPUT
Given f(x)= x^3 + 2x^2 - 4x - 5
Enter lower limit
0
Enter Upper Limit
5
Enter the number of intervals :
100
The Value of integral under the enterd limits is :
122.934
The Total Error is :
-0.0199479
*/
Note - The following programs are coded for Linux (Knoppix) Operating System. For windows do the following changes
change '#include ' to '#include ' & same to all other header files.
Delete 'using namespace std;'.
At the end of main method type return 0;.
Then save it and run it in Turbo C++ or any other software.
Manas SharmaPh.D. researcher at Friedrich-Schiller University Jena, Germany. I’m a physicist specializing in computational material science. I write efficient codes for simulating light-matter interactions at atomic scales. I like to develop Physics, DFT, and Machine Learning related apps and software from time to time. Can code in most of the popular languages. I like to share my knowledge in Physics and applications using this Blog and a YouTube channel.
manas.bragitoff.com/Share this:Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on WhatsApp (Opens in new window)Click to share on Pinterest (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Skype (Opens in new window)Click to email a link to a friend (Opens in new window)Click to print (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Pocket (Opens in new window)Click to share on Telegram (Opens in new window)Like this:Like Loading...

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