/*
    bisec1_2.c: 負領域可能バージョン
 */
#include <stdio.h>

double f(double x)
//  f(x) = x^2 - 2
{
    return x * x - 2.0;
}

int main(void)
{
    int n=0;
    double x1=1, x2=2, x3, err;
    double eps = 1.0e-6;
    char s[128];

    fprintf(stderr, "# x1, x2 = "); fgets(s, 128, stdin);
    sscanf(s, "%lf%lf", &x1, &x2);
    fprintf(stderr, "# eps = "); fgets(s, 128, stdin);
    sscanf(s, "%lf", &eps);
    printf("# n, x, err\n");
    do {
        n++;
        x3 = (x1 + x2) / 2.0;
        if (f(x1)*f(x3) < 0.0) x2 = x3;
        else                   x1 = x3;
        err = x2 - x1;
        printf("%4d, % .15e, % .15e\n", n, x3, err);
    } while (err >= eps);
    printf("\n# sqrt(2) = % .15e\n", (x1 + x2) / 2.0);
    return 0;
}
/*  ---   実行例   ---
Z:\proen1\kadai4>bisec1_2
# x1, x2 = -2 -1
# eps = 1e-10
# n, x, err
   1, -1.500000000000000e+000,  5.000000000000000e-001
   2, -1.250000000000000e+000,  2.500000000000000e-001
   3, -1.375000000000000e+000,  1.250000000000000e-001
   4, -1.437500000000000e+000,  6.250000000000000e-002
   5, -1.406250000000000e+000,  3.125000000000000e-002
   6, -1.421875000000000e+000,  1.562500000000000e-002
   7, -1.414062500000000e+000,  7.812500000000000e-003
   8, -1.417968750000000e+000,  3.906250000000000e-003
   9, -1.416015625000000e+000,  1.953125000000000e-003
  10, -1.415039062500000e+000,  9.765625000000000e-004
  11, -1.414550781250000e+000,  4.882812500000000e-004
  12, -1.414306640625000e+000,  2.441406250000000e-004
  13, -1.414184570312500e+000,  1.220703125000000e-004
  14, -1.414245605468750e+000,  6.103515625000000e-005
  15, -1.414215087890625e+000,  3.051757812500000e-005
  16, -1.414199829101563e+000,  1.525878906250000e-005
  17, -1.414207458496094e+000,  7.629394531250000e-006
  18, -1.414211273193359e+000,  3.814697265625000e-006
  19, -1.414213180541992e+000,  1.907348632812500e-006
  20, -1.414214134216309e+000,  9.536743164062500e-007
  21, -1.414213657379150e+000,  4.768371582031250e-007
  22, -1.414213418960571e+000,  2.384185791015625e-007
  23, -1.414213538169861e+000,  1.192092895507813e-007
  24, -1.414213597774506e+000,  5.960464477539063e-008
  25, -1.414213567972183e+000,  2.980232238769531e-008
  26, -1.414213553071022e+000,  1.490116119384766e-008
  27, -1.414213560521603e+000,  7.450580596923828e-009
  28, -1.414213564246893e+000,  3.725290298461914e-009
  29, -1.414213562384248e+000,  1.862645149230957e-009
  30, -1.414213561452925e+000,  9.313225746154785e-010
  31, -1.414213561918587e+000,  4.656612873077393e-010
  32, -1.414213562151417e+000,  2.328306436538696e-010
  33, -1.414213562267833e+000,  1.164153218269348e-010
  34, -1.414213562326040e+000,  5.820766091346741e-011

# sqrt(2) = -1.414213562355144e+000
*/