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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. #define EPS 1e-5
  5.  
  6. double f(double x) {
  7.     return x*x - 1 - sin(x);
  8. }
  9.  
  10. // 二分法
  11. double bisection(double a, double b) {
  12.     double mid;
  13.  
  14.     while (1) {
  15.         mid = (a + b) / 2.0;
  16.  
  17.         if (fabs(f(mid)) < EPS) return mid;
  18.  
  19.         if (f(a) * f(mid) < 0)
  20.             b = mid;
  21.         else
  22.             a = mid;
  23.     }
  24. }
  25.  
  26. // はさみうち法（False Position）
  27. double false_position(double a, double b) {
  28.     double x;
  29.  
  30.     while (1) {
  31.         x = (a * f(b) - b * f(a)) / (f(b) - f(a));
  32.  
  33.         if (fabs(f(x)) < EPS) return x;
  34.  
  35.         if (f(a) * f(x) < 0)
  36.             b = x;
  37.         else
  38.             a = x;
  39.     }
  40. }
  41.  
  42. int main() {
  43.     double r1, r2;
  44.  
  45.     printf("=== Bisection Method ===\n");
  46.     r1 = bisection(-1.0, 0.0);
  47.     r2 = bisection(1.0, 2.0);
  48.     printf("Roots: %.6f, %.6f\n", r1, r2);
  49.  
  50.     printf("\n=== False Position Method ===\n");
  51.     r1 = false_position(-1.0, 0.0);
  52.     r2 = false_position(1.0, 2.0);
  53.     printf("Roots: %.6f, %.6f\n", r1, r2);
  54.  
  55.     return 0;
  56. }
  57.  
Success #stdin #stdout 0s 5292KB
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=== Bisection Method ===
Roots: -0.636734, 1.409622

=== False Position Method ===
Roots: -0.636732, 1.409622
https://ideone.com/zk0MfY
language:
C (gcc 8.3)
created:
3 hours ago
visibility:
public

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