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  1. #include <iostream>
  2. #include <cmath>
  3. using namespace std;
  4.  
  5.  
  6. double trapez(double(*f)(double), double a, double b, double eps)
  7. {
  8.     double old_i = 0, new_i = old_i+2*eps;
  9.     for(unsigned int n = 1; abs(new_i-old_i) > eps; n *= 2)
  10.     {
  11.         old_i = new_i;
  12.         double h = (b-a)/n, s = -(f(a) + f(b))/2;
  13.         for(int i = 0; i <= n; ++i)
  14.             s += f(a + i*h);
  15.         new_i = s*h;
  16.     }
  17.     return new_i;
  18. }
  19.  
  20. double y(double x) 
  21. { 
  22.     x = log(x)/x/x;
  23.     return sqrt(1+x*x); 
  24. }
  25.  
  26. int main()
  27. {
  28.     cout << trapez(y,1,2.718281828459045,1e-5) << endl;
  29. }
  30.  
Success #stdin #stdout 0.01s 5592KB
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Standard input is empty
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1.7395
https://ideone.com/ncW0bK
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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