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$sin (aggregation)

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Definition定义

$sin

New in version 4.2. 4.2版新增。

Returns the sine of a value that is measured in radians.返回以弧度为单位测量的值的正弦值。

$sin has the following syntax:具有以下语法：

{ $sin: <expression> }

$sin takes any valid expression that resolves to a number. 采用任何解析为数字的有效表达式。If the expression returns a value in degrees, use the $degreesToRadians operator to convert the result to radians.如果表达式返回以度为单位的值，请使用$degreesToRadians运算符将结果转换为弧度。

By default $sin returns values as a double. 默认情况下，$sin以double返回值。$sin can also return values as a 128-bit decimal as long as the <expression> resolves to a 128-bit decimal value.只要<expression>解析为128位十进制值，$sin也可以以128位十进制形式返回值。

For more information on expressions, see Expressions.有关表达式的详细信息，请参阅表达式。

Behavior行为

null, NaN, and +/- Infinity

If the argument resolves to a value of null or refers to a field that is missing, $sin returns null. 如果参数解析为null值或引用了缺失的字段，$sin将返回null。If the argument resolves to NaN, $sin returns NaN. If the argument resolves to negative or positive infinity, $sin throws an error.如果参数解析为NaN，$sin将返回NaN。如果参数解析为负无穷大或正无穷大，$sin将抛出一个错误。

Example示例Results结果
{ $sin: NaN }NaN
{ $sin: null }null
{ $sin : Infinity}
or
{ $sin : -Infinity } 		Throws an error message resembling the following formatted output: 抛出类似以下格式化输出的错误消息：
"errmsg" :
  "Failed to optimize pipeline :: caused by :: cannot
  apply $sin to -inf, value must in (-inf,inf)"

Example实例

Sine of Value in Degrees值的正弦（以度为单位）Sine of Value in Radians正弦值（单位：弧度）

The trigonometry collection contains a document that stores the hypotenuse and one angle in a right-angle triangle:trigonometry集合包含一个文档，该文档存储直角三角形中的斜边和一个角度：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
  "hypotenuse" : NumberDecimal("5")
}

The following aggregation operation uses the $sin expression to calculate the side opposite to angle_a and add it to the input document using the $addFields pipeline stage.下面的聚合操作使用$sin表达式来计算与angle_a相反的一侧，并使用$addFields管道阶段将其添加到输入文档中。

db.trigonometry.aggregate([
  {
    $addFields : {
      "side_b" : {
        $multiply : [
          { $sin : {$degreesToRadians : "$angle_a"} },
          "$hypotenuse"
        ]
      }
    }
  }
])

The $degreesToRadians expression converts the degree value of angle_a to the equivalent value in radians.$degreesToRadians表达式将angle_a的度数值转换为以弧度表示的等效值。

The command returns the following output:该命令返回以下输出：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
  "side_b" : NumberDecimal("4.000000000000000000000000000000000"),
  "hypotenuse" : NumberDecimal("5"),
}

Since angle_a and hypotenuse are stored as 128-bit decimals, the output of $sin is a 128-bit decimal.由于angle_a和hypotenuse存储为128位十进制，因此$sin的输出是128位十进制。

The trigonometry collection contains a document that stores the hypotenuse and one angle in a right-angle triangle:trigonometry集合包含一个文档，该文档存储直角三角形中的斜边和一个角度：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("0.9272952180016122324285124629224288"),
  "hypotenuse" : NumberDecimal("5")
}

The following aggregation operation uses the $sin expression to calculate the side opposite to angle_a and add it to the input document using the $addFields pipeline stage.下面的聚合操作使用$sin表达式来计算与angle_a相反的一侧，并使用$addFields管道阶段将其添加到输入文档中。

db.trigonometry.aggregate([
  {
    $addFields : {
      "side_b" : {
        $multiply : [
          { $sin : "$angle_a" },
          "$hypotenuse"
        ]
      }
    }
  }
])

The command returns the following output:该命令返回以下输出：

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("0.9272952180016122324285124629224288"),
  "side_b" : NumberDecimal("4.000000000000000000000000000000000"),
  "hypotenuse" : NumberDecimal("5"),
}

Since angle_a and hypotenuse are stored as 128-bit decimals, the output of $sin is a 128-bit decimal.由于angle_a和hypotenuse存储为128位十进制，因此$sin的输出是128位十进制。