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tan |
Portability: | ISO/ANSI C conforming, UNIX compatible |
SYNOPSIS | |
DESCRIPTION | |
RETURN VALUE | |
DIAGNOSTICS | |
EXAMPLE | |
RELATED FUNCTIONS | |
SEE ALSO |
SYNOPSIS |
#include <math.h> double tan(double x);
DESCRIPTION |
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 is used to compute the tangent. If
x
is very large, only a limited precision is left to represent x mod
2 . Thus, an error message is written for very large negative or positive
arguments (see DIAGNOSTICS).
RETURN VALUE |
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.
DIAGNOSTICS |
The tangent is not defined if
x
is ± /2, ± 3 /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 /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.
EXAMPLE |
#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) = %f\n", YVAL, cotan); }
RELATED FUNCTIONS |
SEE ALSO |
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