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$cos (expression operator)

Definition

$cos

Returns the cosine of a value that is measured in radians.

$cos has the following syntax:

{ $cos: <expression> }

$cos takes any valid expression that resolves to a number. If the expression returns a value in degrees, use the $degreesToRadians operator to convert the result to radians.

By default $cos returns values as a double. $cos 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

`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.

Example

Results

{ $cos: NaN }

NaN

{ $cos: null }

null

{ $cos : Infinity}

{ $cos : -Infinity }

Throws an error message resembling the following formatted output:

"errmsg" :
 "Failed to optimize pipeline :: caused by :: cannot
 apply $cos to -inf, value must in (-inf,inf)"

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.

Back

$convert

$cosh

Definition

Behavior

null, NaN, and +/- Infinity

Example

`null`, `NaN`, and `+/- Infinity`