Mathc initiation/a176

Sommaire

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	s_an.h

/* --------------------------------- */
/* save as s_an.h                    */
/* --------------------------------- */
double S_an(
int n,
int a_1,
int r)
{
        return(     a_1*n + (((n-1)*r)*n)/2 );
}
char  S_aneq[] =  "[a_1 n + [(n-1)*r)*n] /2";
/* --------------------------------- */
/* --------------------------------- */
/*  Compute the partial sum of the sequence a_n = a1 + (n-1) r


   S_n = [ a1]        + [ a1+     r] + ... + [ a1+(n-2)r] + [ a1+(n-1)r]   
   S_n = [ a1+(n-1)r] + [ a1+(n-2)r] + ... + [ a1+     r] + [ a1]    
      -------------------------------------------------
 2 S_n = [2a1+(n-1)r] + [2a1+(n-1)r] + ... + [2a1+(n-1)r] + [2a1+(n-1)r]
     
                                                                              
 2 S_n = [(2a1)n + ((n-1)r)n ] 
 
 
   S_n = [ (a1)n + ((n-1)r)n]  
                   ---------
                      2
*/                              
/* --------------------------------- */
/* --------------------------------- */

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