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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. double ATAN(double x);
  5.  
  6. int main(){
  7.     double a;
  8.     a = 4*(4 * ATAN(1.0/5.0) - ATAN( 1.0 / 239.0));
  9.     printf("%.11lf", a);
  10.  
  11.     return 0;
  12. }
  13.  
  14. double ATAN(double x){
  15.     double y;
  16.     double t, s;
  17.     int n;
  18.  
  19.     y = x;
  20.     t = x;
  21.     n = 3;
  22.     while( 1 ){
  23.         t = - t*x*x;
  24.         s = t/n;
  25.         if(fabs(s) < 0.000000000001) break;
  26.         y = y + s;
  27.         n++; n++;
  28.     }
  29.     return y;
  30. }
Success #stdin #stdout 0.01s 1720KB
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3.14159265359
https://ideone.com/cebSY
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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