#include <math.h> double tan(double x);
tan
computes the trigonometric tangent of an argument x
expressed
in radians.
Because the tangent function is periodic, only the value of x mod 2 pi is used
to compute the tangent. If x
is very large, only a limited precision is
left to represent x mod 2 pi. Thus, an error message is written for very large
negative or positive arguments (see DIAGNOSTICS).
tan
returns the value of the tangent of the argument x
,
provided that this value is defined and computable. The return value is a
double-precision, floating-point number.
x
is +- pi/2, +-3pi/2,
or any other value of the following form:
pi/2 + n(pi)n is an integer.
If the value of x
is so close to an odd multiple of pi/2 that the
tangent cannot be represented accurately, the function returns HUGE_VAL
.
The run-time library writes an error message to stderr
(the standard
error file).
If the value of x
is greater than 6.7465e9, the function returns 0.0. In
this case, the message "total loss of significance" is also written to
stderr
.
If an error occurs in tan
, the _matherr
routine is called.
You can supply your own version of _matherr
to suppress the diagnostic
message or modify the value returned.
#include <stdio.h> #include <math.h> #define YVAL 1.04 main() { double cotan; /* The cotangent is 1 divided by the */ /* tangent of YVAL. */ cotan = 1 / tan(YVAL); printf("1 / tan(%f) = %fn", YVAL, cotan); }
cos
, _matherr
, sin
Copyright (c) 1998 SAS Institute Inc. Cary, NC, USA. All rights reserved.