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$cos
New in version 4.2.在版本4.2中新增。
Returns the cosine of a value that is measured in radians.返回以弧度度量的值的余弦。
$cos has the following syntax:语法如下：
{ $cos: <expression> }
$cos takes any valid expression that resolves to a number. 接受解析为数字的任何有效表达式。If the expression returns a value in degrees, use the 如果表达式返回以度为单位的值，请使用$degreesToRadians operator to convert the result to radians.$degreesToRadians运算符将结果转换为弧度。
By default 默认情况下，$cos returns values as a double. $cos以double返回值。$cos can also return values as a 128-bit decimal as long as the <expression> resolves to a 128-bit decimal value.<expression>解析为128位十进制值，$cos也可以以128位十进制返回值。
For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。
null, NaN, and +/- InfinityIf the argument resolves to a value of 如果参数解析为null or refers to a field that is missing, $cos returns null. null值或引用缺少的字段，$cos将返回null。If the argument resolves to 如果参数解析为NaN, $cos returns NaN. NaN，$cos返回NaN。If the argument resolves to negative or positive infinity, 如果参数解析为负或正无穷大，$cos throws an error.$cos将抛出错误。
{ $cos: NaN } | NaN |
{ $cos: null } | null |
or
|
"errmsg" : "Failed to optimize pipeline :: caused by :: cannot apply $cos to -inf, value must in (-inf,inf)" |
The trigonometry collection contains a document that
stores the hypotenuse and one angle in a right-angle triangle:
{
"_id" : ObjectId("5c50782193f833234ba90d85"),
"angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
"hypotenuse" : NumberDecimal("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" : NumberDecimal("53.13010235415597870314438744090659"),
"side_a" : NumberDecimal("2.999999999999999999999999999999999"),
"hypotenuse" : NumberDecimal("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" : NumberDecimal("0.9272952180016122324285124629224288"),
"hypotenuse" : NumberDecimal("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" : NumberDecimal("0.9272952180016122324285124629224288"),
"side_b" : NumberDecimal("3.000000000000000000000000000000000"),
"hypotenuse" : NumberDecimal("5"),
}Since angle_a and hypotenuse are stored as
128-bit decimals, the output of
$cos is a 128-bit decimal.