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  1. #include <iostream>
  2. #include <cmath>
  3.  
  4. using namespace std;
  5.  
  6. double up = 19.0 + (61.0/125.0);
  7. double down = -32.0 - (2.0/3.0);
  8. double rectangle = (up - down) * 8.0;
  9.  
  10. double f(double x) {
  11.     return (pow(x, 4.0)/500.0) - (pow(x, 2.0)/200.0) - 0.012;
  12. }
  13.  
  14. double g(double x) {
  15.     return -(pow(x, 3.0)/30.0) + (x/20.0) + (1.0/6.0);
  16. }
  17.  
  18. double area_upper(double x, double step) {
  19.     return (((up - f(x)) + (up - f(x + step))) * step) / 2.0;
  20. }
  21.  
  22. double area_lower(double x, double step) {
  23.     return (((g(x) - down) + (g(x + step) - down)) * step) / 2.0;
  24. }
  25.  
  26. double area(double x, double step) {
  27.     return area_upper(x, step) + area_lower(x, step);
  28. }
  29.  
  30. int main() {
  31.     double current = 0, last = 0, step = 1.0;
  32.  
  33.     do {
  34.         last = current;
  35.         step /= 10.0;
  36.         current = 0;
  37.  
  38.         for(double x = 2.0; x < 10.0; x += step) current += area(x, step);
  39.  
  40.         current = rectangle - current;
  41.         current = round(current * 1000.0) / 1000.0;
  42.         //cout << current - last << endl;
  43.     } while( std::fabs(current - last) >= 1e-8);
  44.  
  45.     cout << current << endl;
  46.     return 0;
  47. }
Success #stdin #stdout 0.03s 3096KB
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https://ideone.com/kUqhhf
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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