$acosh (aggregation)¶
$acosh
¶New in version 4.2.
Returns the inverse hyperbolic cosine (hyperbolic arc cosine) of a value.
$acosh
has the following syntax:{ $acosh: <expression> } $acosh
takes any valid expression that resolves to a number between1
and+Infinity
, e.g.1 <= value <= +Infinity
.$acosh
returns values in radians. Use$radiansToDegrees
operator to convert the output value from radians to degrees.By default
$acosh
returns values as adouble
.$acosh
can also return values as a 128bit decimal as long as the<expression>
resolves to a 128bit decimal value.For more information on expressions, see Expressions.
Behavior¶
null
, NaN
, and +/ Infinity
¶
If the argument resolves to a value of null
or refers to a field
that is missing, $acosh
returns null
. If the argument
resolves to NaN
, $acosh
returns NaN
. If the
argument resolves to negative infinity, $acosh
throws an
error. If the argument resolves to Infinity
, $acosh
returns Infinity
. If the argument resolves to a value outside the
bounds of [1, Infinity]
inclusive, $acosh
throws an error.
Example  Results  

{ $acosh: NaN }  NaN  
{ $acosh: null }  null  
{ $acosh : Infinity}  Infinity  
{ $acosh : 0 }  Throws an error message resembling the following formatted output:

Example¶
The trigonometry
collection contains a document that
stores a value along the x
axis of a 2D graph:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "xcoordinate" : NumberDecimal("3") }
The following aggregation operation uses the
$acosh
expression to calculate inverse hyperbolic
cosine of xcoordinate
and add it to the input document using
the $addFields
pipeline stage.
db.trigonometry.aggregate([ { $addFields : { "ycoordinate" : { $radiansToDegrees : { $acosh : "$xcoordinate" } } } } ])
The $radiansToDegrees
expression converts the
radian value returned by $acosh
to the equivalent
value in degrees.
The command returns the following output:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "xcoordinate" : NumberDecimal("3"), "ycoordinate" : NumberDecimal("100.9979734210524228844295260083432") }
Since xcoordinate
is stored as a
128bit decimal, the output of
$acosh
is a 128bit decimal.