float cosf (float x); 
float tandf (float x); 

long double cosl (long double x); 
long double tandl (long double x); 

#include <errno.h> 
#include <math.h> 
#include <stdio.h> 
 
main() 
{ 
   double input, square_root; 
 
   printf("Enter a number: "); 
   scanf("%le", &input); 
   errno = 0; 
   square_root = sqrt(input); 
 
   if (errno == EDOM) 
      perror("Input was negative"); 
   else 
      printf("Square root of %e = %e\n", 
              input, square_root); 
} 

$ CREATE IEEE_INFINITY.C 
#include <fp.h> 
 
double my_huge_val = HUGE_VAL 
^Z 
$ CC /FLOAT=IEEE/IEEE=DENORM IEEE_INFINITY 
 
double my_huge_val = HUGE_VAL; 
.....................^ 
%CC-E-NEEDCONSTEXPR, In the initializer for my_huge_val, "decc$gt_dbl_infinity" 
is not constant, but occurs in a context that requires a constant expression. 
at line number 3 in file WORK1$:[RTL]IEEE_INFINITY.C;1 
$ 

/*        CHAP_7_MATH_EXAMPLE.C                                 */ 
 
/* This example uses two functions --- mytan and main ---       */ 
/* to calculate the tangent value of a number, and to check     */ 
/* the calculation using the sin and cos functions.             */ 
 
#include <math.h> 
#include <stdio.h> 
 
/* This function calculates the tangent using the sin and       */ 
/* cos functions.                                               */ 
 
double mytan(x) 
    double x; 
{ 
    double y, 
           y1, 
           y2; 
 
    y1 = sin(x); 
    y2 = cos(x); 
 
    if (y2 == 0) 
        y = 0; 
    else 
        y = y1 / y2; 
 
    return y; 
} 
main() 
{ 
    double x; 
 
    /*  Print values: compare   */ 
    for (x = 0.0; x < 1.5; x += 0.1) 
        printf("tan of %4.1f = %6.2f\t%6.2f\n", x, mytan(x), tan(x)); 
} 

$ RUN  EXAMPLE
tan of  0.0 =   0.00      0.00
tan of  0.1 =   0.10      0.10
tan of  0.2 =   0.20      0.20
tan of  0.3 =   0.31      0.31
tan of  0.4 =   0.42      0.42
tan of  0.5 =   0.55      0.55
tan of  0.6 =   0.68      0.68
tan of  0.7 =   0.84      0.84
tan of  0.8 =   1.03      1.03
tan of  0.9 =   1.26      1.26
tan of  1.0 =   1.56      1.56
tan of  1.1 =   1.96      1.96
tan of  1.2 =   2.57      2.57
tan of  1.3 =   3.60      3.60
tan of  1.4 =   5.80      5.80
$