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kazi_omar

Nov 2nd, 2021 (edited)

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//example 5.9
#include <bits/stdc++.h>
using namespace std;
float expression(float x)
{
return 1 / (1 + x);
}
float lower, upper, integration = 0.0, stepSize, k;
int subInterval;
float third()
{
for (int i = 1; i <= subInterval - 1; i++)
{
k = lower + i * stepSize;
if (i % 2 == 0)
{
integration = integration + 2 * (expression(k));
}
else
{
integration = integration + 4 * (expression(k));
}
}
integration = integration * stepSize / 3;
return integration;
}
float eighth()
{
for (int i = 1; i <= subInterval - 1; i++)
{
k = lower + i * stepSize;
if (i % 3 == 0)
{
integration = integration + 2 * (expression(k));
}
else
{
integration = integration + 3 * (expression(k));
}
}
integration = integration * stepSize * 3.0 / 8.0;
return integration;
}
float trapezoidal()
{
for (int i = 1; i <= subInterval - 1; i++)
{
k = lower + i * stepSize;
integration = integration + 2 * (expression(k));
}
integration = integration * stepSize / 2;
return integration;
}
int main()
{
cin >> lower >> upper >> subInterval;
stepSize = (upper - lower) / subInterval;
integration = expression(lower) + expression(upper);
cout << "Required value of integration for 3rd rule is: " << third() << endl;
cout << "Required value of integration for eighth rule is: " << eighth() << endl;
cout << "Required value of integration for trapezoidal rule is: " << trapezoidal() << endl;
return 0;
}

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