#include <math.h>

       double tan(double x);
       float tanf(float x);
       long double tanl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       tanf(), tanl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

       The tan() function returns the tangent of x, where x is given in  radi-

       On success, these functions return the tangent of x.

       If x is a NaN, a NaN is returned.

       If  x is positive infinity or negative infinity, a domain error occurs,
       and a NaN is returned.

       If the correct result would overflow, a range  error  occurs,  and  the
       functions  return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with
       the mathematically correct sign.

       See math_error(7) for information on how to determine whether an  error
       has occurred when calling these functions.

       The following errors can occur:

       Domain error: x is an infinity
              errno  is set to EDOM (but see BUGS).  An invalid floating-point
              exception (FE_INVALID) is raised.

       Range error: result overflow
              An overflow floating-point exception (FE_OVERFLOW) is raised.

       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
       4.3BSD, C89.

       Before version 2.10, the glibc implementation did not set errno to EDOM
       when a domain error occurred.
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