Docs Home → Develop Applications → MongoDB Manual
$acos (aggregation)![](/docs/v5.2/assets/link.svg)
$acos
New in version 4.2.
Returns the inverse cosine (arc cosine) of a value.
$acos
has the following syntax:{ $acos: <expression> } $acos
takes any valid expression that resolves to a number between-1
and1
, e.g.-1 <= value <= 1
.$acos
returns values in radians. Use$radiansToDegrees
operator to convert the output value from radians to degrees.By default
$acos
returns values as adouble
.$acos
can also return values as a 128-bit decimal as long as the<expression>
resolves to a 128-bit decimal value.For more information on expressions, see Expressions.
Behavior![](/docs/v5.2/assets/link.svg)
If the argument resolves to a value of null
or refers to a field
that is missing, $acos
returns null
. If the
argument resolves to NaN
, $acos
returns NaN
.
If the argument resolves to a value outside the bounds of
[-1, 1]
inclusive, $acos
throws an error.
Example | Results | |||
---|---|---|---|---|
{ $acos: NaN } | NaN | |||
{ $acos: null } | null | |||
or
| Throws an error message resembling the following formatted output:
|