Definition
$cosReturns the cosine of a value that is measured in radians.
$coshas the following syntax:{ $cos: <expression> }$costakes any valid expression that resolves to a number. If the expression returns a value in degrees, use the$degreesToRadiansoperator to convert the result to radians.By default
$cosreturns values as adouble.$coscan 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
null, NaN, and +/- Infinity
If the argument resolves to a value of null or refers to a field that is missing, $cos returns null. If the argument resolves to NaN, $cos returns NaN. If the argument resolves to negative or positive infinity, $cos throws an error.
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Example
The trigonometry collection contains a document that stores the hypotenuse and one angle in a right-angle triangle:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "angle_a" : Decimal128("53.13010235415597870314438744090659"), "hypotenuse" : Decimal128("5")}The following aggregation operation uses the $cos expression to calculate the side adjacent to angle_a and add it to the input document using the $addFields pipeline stage.
db.trigonometry.aggregate([ { $addFields : { "side_a" : { $multiply : [ { $cos : {$degreesToRadians : "$angle_a"} }, "$hypotenuse" ] } } }])The $degreesToRadians expression converts the degree value of angle_a to the equivalent value in radians.
The command returns the following output:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "angle_a" : Decimal128("53.13010235415597870314438744090659"), "side_a" : Decimal128("2.999999999999999999999999999999999"), "hypotenuse" : Decimal128("5"),}Since angle_a and hypotenuse are stored as 128-bit decimals, the output of $cos is a 128-bit decimal.
The trigonometry collection contains a document that stores the hypotenuse and one angle in a right-angle triangle:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "angle_a" : Decimal128("0.9272952180016122324285124629224288"), "hypotenuse" : Decimal128("5")}The following aggregation operation uses the $cos expression to calculate the side adjacent to angle_a and add it to the input document using the $addFields pipeline stage.
db.trigonometry.aggregate([ { $addFields : { "side_b" : { $multiply : [ { $cos : "$angle_a" }, "$hypotenuse" ] } } }])The command returns the following output:
{ "_id" : ObjectId("5c50782193f833234ba90d85"), "angle_a" : Decimal128("0.9272952180016122324285124629224288"), "side_b" : Decimal128("3.000000000000000000000000000000000"), "hypotenuse" : Decimal128("5"),}Since angle_a and hypotenuse are stored as 128-bit decimals, the output of $cos is a 128-bit decimal.