Section (3) atan
atan, atanf, atanl — arc tangent function
||long double x
These functions calculate the principal value of the arc
x; that is
the value whose tangent is
On success, these functions return the principal value of
the arc tangent of
in radians; the return value is in the range [−pi/2,
x is a NaN, a
NaN is returned.
x is +0
(−0), +0 (−0) is returned.
x is positive
infinity (negative infinity), +pi/2 (−pi/2) is
For an explanation of the terms used in this section, see attributes(7).
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
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386BSD man pages
Modified 1993-07-24 by Rik Faith (faithcs.unc.edu)
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