Returns the arc cosine of the argument.
math:acos( $arg as xs:double?xs:double?If $arg is the empty sequence, the function returns the empty sequence.
Otherwise the result is the arc cosine of $arg, as defined in the specification of the
acos function applied to 64-bit binary floating point values.
The result is in the range zero to +π radians.
The expression math:acos(()) returns ().
The expression math:acos(0) returns 1.5707963267948966e0.
The expression math:acos(-0.0e0) returns 1.5707963267948966e0.
The expression math:acos(1.0e0) returns 0.0e0.
The expression math:acos(-1.0e0) returns 3.141592653589793e0.
The expression math:acos(2.0e0) returns xs:double('NaN').
The expression math:acos(xs:double('NaN')) returns xs:double('NaN').
The expression math:acos(xs:double('INF')) returns xs:double('NaN').
The expression math:acos(xs:double('-INF')) returns xs:double('NaN').
The treatment of the invalidOperation exception is defined in .
If $arg is NaN, or if its absolute value is greater than one,
then the result is NaN.
In other cases the result is an xs:double value representing an angle
θ in radians in the range 0 <=
θ
<=
+
π.