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$acosh (aggregation)

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$acosh

New in version 4.2.

Returns the inverse hyperbolic cosine (hyperbolic arc cosine) of a value.

$acosh has the following syntax:

{ $acosh: <expression> }

$acosh takes any valid expression that resolves to a number between 1 and +Infinity, e.g. 1 <= value <= +Infinity.

$acosh returns values in radians. Use $radiansToDegrees operator to convert the output value from radians to degrees.

By default $acosh returns values as a double. $acosh 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, $acosh returns null. If the argument resolves to NaN, $acosh returns NaN. If the argument resolves to negative infinity, $acosh throws an error. If the argument resolves to Infinity, $acosh returns Infinity. If the argument resolves to a value outside the bounds of [-1, Infinity] inclusive, $acosh throws an error.

ExampleResults
{ $acosh: NaN }NaN
{ $acosh: null }null
{ $acosh : Infinity}Infinity
{ $acosh : 0 }Throws an error message resembling the following formatted output: 
"errmsg" :
  "Failed to optimize pipeline :: caused by :: cannot
  apply $acosh to -inf, value must in (1,inf)"

Example