$asin (aggregation)
New in version 4.2.
Returns the inverse sine (arc sine) of a value.
$asin
has the following syntax:
- { $asin: <expression> }
$asin
takes any valid expression that resolves to a number between -1
and 1
, e.g. -1 <= value <= 1
.
$asin
returns values in radians. Use$radiansToDegrees
operator to convert the output valuefrom radians to degrees.
By default $asin
returns values as a double
.$asin
can also return values as a128-bit decimalas long as the <expression>
resolves to a 128-bit decimal value.
For more information on expressions, seeExpressions.
Behavior
If the argument resolves to a value of null
or refers to a fieldthat is missing, $asin
returns null
. If theargument resolves to NaN
, $asin
returns NaN
.If the argument resolves to a value outside the bounds of[-1, 1]
inclusive, $asin
throws an error.
Example | Results |
---|---|
{ $asin: NaN } | NaN |
{ $asin: null } | null |
{ $asin : Infinity} or{ $asin : -Infinity } | Throws an error message resembling the following formattedoutput:
|
Example
- Inverse Sine of Value in Degrees
- Inverse Sine of Value in Radians
The trigonometry
collection contains a document thatstores three sides of a right-angle triangle:
- {
- "_id" : ObjectId("5c50782193f833234ba90d85"),
- "side_a" : NumberDecimal("3"),
- "side_b" : NumberDecimal("4"),
- "hypotenuse" : NumberDecimal("5")
- }
The following aggregation operation uses the$asin
expression to calculate the angle oppositeto side_a
and add it to the input document using the$addFields
pipeline stage.
- db.trigonometry.aggregate([
- {
- $addFields : {
- "angle_a" : {
- $radiansToDegrees : {
- $asin : {
- $divide : [ "$side_a", "$hypotenuse" ]
- }
- }
- }
- }
- }
- ])
The $radiansToDegrees
expression converts theradian value returned by $asin
to the equivalentvalue in degrees.
The command returns the following output:
- {
- "_id" : ObjectId("5c50782193f833234ba90d85"),
- "side_a" : NumberDecimal("3"),
- "side_b" : NumberDecimal("4"),
- "hypotenuse" : NumberDecimal("5"),
- "angle_a" : NumberDecimal("36.86989764584402129685561255909341")
- }
Since side_a
and hypotenuse
are stored as128-bit decimals, the output of$asin
is a 128-bit decimal.
The trigonometry
collection contains a document thatstores three sides of a right-angle triangle:
- {
- "_id" : ObjectId("5c50782193f833234ba90d85"),
- "side_a" : NumberDecimal("3"),
- "side_b" : NumberDecimal("4"),
- "hypotenuse" : NumberDecimal("5")
- }
The following aggregation operation uses the$asin
expression to calculate the angle adjacentto side_a
and add it to the input document using the$addFields
pipeline stage.
- db.trigonometry.aggregate([
- {
- $addFields : {
- "angle_a" : {
- $asin : {
- $divide : [ "$side_a", "$hypotenuse" ]
- }
- }
- }
- }
- ])
The command returns the following output:
- {
- "_id" : ObjectId("5c50782193f833234ba90d85"),
- "side_a" : NumberDecimal("3"),
- "side_b" : NumberDecimal("4"),
- "hypotenuse" : NumberDecimal("5"),
- "angle_a" : NumberDecimal("0.6435011087932843868028092287173226")
- }
Since side_a
and hypotenuse
are stored as128-bit decimals, the output of$asin
is a 128-bit decimal.