Returns a double value that is the tangent of its radian
    argument.

    Format

      #include  <math.h>

      double tan  (double x);

      float tanf  (float x); (Integrity servers, Alpha)

      long double tanl  (long double x); (Integrity servers, Alpha)

      double tand  (double x); (Integrity servers, Alpha)

      float tandf  (float x); (Integrity servers, Alpha)

      long double tandl  (long double x); (Integrity servers, Alpha)

1  –  Argument

 x

    A radian expressed as a real number.

2  –  Description

    The tan functions compute the tangent of x, measured in radians.

    The tand functions compute the tangent of x, measured in degrees.

3  –  Return Values

    x                  The tangent of the argument.
    HUGE_VAL           x is a singular point ( . . . -3pi/2, -pi/2,
                       pi/2 . . . ).
    NaN                x is NaN; errno is set to EDOM.
    0                  x is Infinity; errno is set to EDOM.
    HUGE_VAL           Overflow occurred; errno is set to ERANGE.
    0                  Underflow occurred; errno is set to ERANGE.