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  1. #include <stdio.h>
  2. #include <math.h>
  3.  
  4. #define nmax 100
  5. #define pi atan(1.0)*4.0
  6. #define xa 1.0 // 積分範囲_下限
  7. #define xb exp(2) // 積分範囲_上弦
  8. #define h  0.5 // 刻み幅
  9.  
  10. double f( double );
  11. double Sdai( int ni,double y[] );
  12.  
  13. int main(void)
  14. {
  15.   double S,Sd,Err_d;
  16.   double xt[nmax],yt[nmax];
  17.   int i,j,l,ni;
  18.  
  19.   /** きざみ幅 **/
  20.   ni=(xb-xa)/h;
  21.  
  22.   /** 初期値の代入 **/
  23.   for(i=0; i<=ni; i++){
  24.     xt[i] = xa + i*h;
  25.     yt[i] = f(xt[i]);
  26.     printf("%12.9f, %12.9f \n", xt[i], yt[i]); 
  27.   }
  28.  
  29.   /** 面積の計算 **/
  30.   S=6*(pow(exp(1),2)-(1/4)pow(exp(1),4)+1/4); // 真値
  31.   Sd=Sdai(ni,yt);
  32.   Err_d=fabs(Sd-S);
  33.  
  34.   /** 計算結果の出力 **/
  35.   printf("  きざみ幅        真値         台形 \n");
  36.   printf("%12.9f  %12.9f  %12.9f  %12.9f   \n",h,S,Sd,Err_d);  
  37. }  
  38.  
  39. /** 積分関数 **/
  40. double f(double xx)
  41. {
  42.   return 6*x*log(x);
  43. }
  44.  
  45. /** 台形公式による積分 **/
  46. double Sdai(int ni,double y[])
  47. {
  48.   double S;
  49.   int l;
  50.  
  51.   S=0.0;
  52.   for(l=1; l<ni; l++) S+=2.0*y[l];
  53.   S=(S+y[0]+y[ni])*h/2.0;
  54.   return S;
  55. }
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
prog.c:30:27: error: expected ')'
  S=6*(pow(exp(1),2)-(1/4)pow(exp(1),4)+1/4); // 真値
                          ^
prog.c:30:7: note: to match this '('
  S=6*(pow(exp(1),2)-(1/4)pow(exp(1),4)+1/4); // 真値
      ^
prog.c:42:12: error: use of undeclared identifier 'x'
  return 6*x*log(x);
           ^
prog.c:42:18: error: use of undeclared identifier 'x'
  return 6*x*log(x);
                 ^
3 errors generated.
stdout
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Standard output is empty
https://ideone.com/gNxGwc
language:
C (clang 8.0)
created:
5 years ago
visibility:
public

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