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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. int main(void) {
  5.   double a = 0.0, b = 4.0, m;
  6.   double fa, fb, fm;
  7.   double x = 3.0, fx, dfx, xn;
  8.   double min = 1e-6;
  9.   int ia = 0, ib = 0;
  10.  
  11.   fa = cos(a/2.0);
  12.   fb = cos(b/2.0);
  13.  
  14.   // 二分法
  15.   while (1) {
  16.     m  = (a + b) / 2.0;
  17.     fm = cos(m/2.0);
  18.     ia++;
  19.     if (fabs(fm) < min) break;
  20.     if (fa * fm < 0.0) {
  21.       b  = m;
  22.       fb = fm;
  23.     } else {
  24.       a  = m;
  25.       fa = fm;
  26.     }
  27.   }
  28.  
  29.   // ニュートン法
  30.   while (1) {
  31.     fx   = cos(x/2.0);
  32.     dfx  = -0.5 * sin(x/2.0);
  33.     ib++;
  34.     xn = x - fx/dfx;
  35.     x      = xn;
  36.     if (fabs(cos(x/2.0)) < min) break;
  37.   }
  38.  
  39.   printf("二分法の反復回数 = %d\n", ia);
  40.   printf("ニュートン法の反復回数 = %d\n", ib);
  41.  
  42.   return 0;
  43. }
  44.  
Success #stdin #stdout 0s 5312KB
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二分法の反復回数 = 19
ニュートン法の反復回数 = 2
https://ideone.com/i94pdp
language:
C (gcc 8.3)
created:
6 days ago
visibility:
public

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