$asinReturns the inverse sine (arc sine) of a value.
$asinhas the following syntax:{ $asin: <expression> }$asintakes any valid expression that resolves to a number between-1and1, e.g.-1 <= value <= 1.$asinreturns values in radians. Use$radiansToDegreesoperator to convert the output value from radians to degrees.By default
$asinreturns values as adouble.$asincan 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
If the argument resolves to a value of null or refers to a field that is missing, $asin returns null. If the argument resolves to NaN, $asin returns NaN. If the argument resolves to a value outside the bounds of [-1, 1] inclusive, $asin throws an error.
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Example
The trigonometry collection contains a document that stores three sides of a right-angle triangle:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "side_a" : Decimal128("3"), "side_b" : Decimal128("4"), "hypotenuse" : Decimal128("5")}The following aggregation operation uses the $asin expression to calculate the angle opposite to 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 the radian value returned by $asin to the equivalent value in degrees.
The command returns the following output:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "side_a" : Decimal128("3"), "side_b" : Decimal128("4"), "hypotenuse" : Decimal128("5"), "angle_a" : Decimal128("36.86989764584402129685561255909341")}Since side_a and hypotenuse are stored as 128-bit decimals, the output of $asin is a 128-bit decimal.
The trigonometry collection contains a document that stores three sides of a right-angle triangle:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "side_a" : Decimal128("3"), "side_b" : Decimal128("4"), "hypotenuse" : Decimal128("5")}The following aggregation operation uses the $asin expression to calculate the angle adjacent to 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" : Decimal128("3"), "side_b" : Decimal128("4"), "hypotenuse" : Decimal128("5"), "angle_a" : Decimal128("0.6435011087932843868028092287173226")}Since side_a and hypotenuse are stored as 128-bit decimals, the output of $asin is a 128-bit decimal.