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@@ -3,9 +3,37 @@ layout: doc
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+# COSH function
+## Overview
+COSH is a function of the Math and Trigonometry category that calculates the hyperbolic cosine of a number.
+## Usage
+### Syntax
+**COSH(<span title="Number" style="color:#1E88E5">number</span>) => <span title="Number" style="color:#1E88E5">cosh</span>**
+### Argument descriptions
+* *number* ([number](/features/value-types#numbers), required). The hyperbolic angle whose hyperbolic cosine is to be calculated, expressed in radians.
+### Additional guidance
+The formula for the hyperbolic cosine is:
+$$
+\text{cosh(x)} = \dfrac{e^x+e^{-x}}{2}
+$$
+### Returned value
+COSH returns a real [number](/features/value-types#numbers) that is the hyperbolic cosine of the specified hyperbolic angle.
+### Error conditions
+* In common with many other IronCalc functions, COSH propagates errors that are found in its argument.
+* If no argument, or more than one argument, is supplied, then COSH returns the [`#ERROR!`](/features/error-types.md#error) error.
+* If the value of the *number* argument is not (or cannot be converted to) a [number](/features/value-types#numbers), then COSH returns the [`#VALUE!`](/features/error-types.md#value) error.
+* For some argument values, COSH may return a [`#DIV/0!`](/features/error-types.md#div-0) error.
+<!--@include: ../markdown-snippets/error-type-details.txt-->
+## Details
+* The COSH function utilizes the *cosh()* method provided by the [Rust Standard Library](https://doc.rust-lang.org/std/).
+* The figure below illustrates the COSH function.
+<center><img src="/functions/images/hyperboliccosine-curve.png" width="350" alt="Graph showing cosh(x)."></center>
 
-# COSH
+## Examples
+[See some examples in IronCalc](https://app.ironcalc.com/?example=cosh).
 
-::: warning
-🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-:::
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+## Links
+* For more information about hyperbolic functions, visit Wikipedia's [Hyperbolic functions](https://en.wikipedia.org/wiki/Hyperbolic_functions) page.
+* See also IronCalc's [SINH](/functions/math_and_trigonometry/sinh), [COS](/functions/math_and_trigonometry/cos) and [TAN](/functions/math_and_trigonometry/tan) functions.
+* Visit Microsoft Excel's [COSH function](https://support.microsoft.com/en-us/office/cosh-function-e460d426-c471-43e8-9540-a57ff3b70555) page.
+* Both [Google Sheets](https://support.google.com/docs/answer/3093477) and [LibreOffice Calc](https://wiki.documentfoundation.org/Documentation/Calc_Functions/COSH) provide versions of the COSH function.
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