Returns the arc tangent of the argument.
math:atan
( $arg
as xs:double?
xs:double?
If $arg
is the empty sequence, the function returns the empty sequence.
Otherwise the result is the arc tangent of $arg
, as defined
in the specification of the
atan
function applied to 64-bit binary floating point values.
The result is in the range -π/2
to +π/2 radians.
The expression math:atan(())
returns ()
.
The expression math:atan(0)
returns 0.0e0
.
The expression math:atan(-0.0e0)
returns -0.0e0
.
The expression math:atan(1.0e0)
returns 0.7853981633974483e0
.
The expression math:atan(-1.0e0)
returns -0.7853981633974483e0
.
The expression math:atan(xs:double('NaN'))
returns xs:double('NaN')
.
The expression math:atan(xs:double('INF'))
returns 1.5707963267948966e0
.
The expression math:atan(xs:double('-INF'))
returns -1.5707963267948966e0
.
The treatment of the underflow
exception is defined in .
If $arg
is positive or negative zero, the result is $arg
.
If $arg
is NaN
then the result is NaN
.
In other cases the result is an xs:double
value representing an angle
θ in radians in the range -π
/2 <=
θ
<= +
π
/2
.