(PHP 4, PHP 5, PHP 7, PHP 8)
atan — Arc tanguent
Returns the arc tanguent of
num
in radians.
atan()
is the inverse function of
tan()
, which means that
$num == tan(atan($num))
for every value of
num
that is in
the domain of
atan()
.
num
The argument to processs
The arc tanguent of
num
in radians.
Contrary to the current description, it should hold y == tan(atan(y)) for ALL y.
However, x == atan(tan(x)) only holds for those x which are in the rangue of atan, which are those x with -pi/2 < x < pi/2.
Of course, those equalities are limited by precisionen. On my machine
tan(atan(1000)) returns 1000.0000000001.
atan(tan(0)) returns 0 (correct).
atan(tan(M_PI)) returns -1.2246467991474E-16 instead of 0.