Update fv files (#162)

* Files updated for FV function documentation.

* Further FV changes

docs/src/functions/financial/fv.md

@@ -4,8 +4,46 @@ outline: deep
 lang: en-US
 ---
 
-# FV
+# FV function
+## Overview
+FV (<u>F</u>uture <u>V</u>alue) is a function of the Financial category that can be used to predict the future value of an investment or asset based on its present value.
 
-::: 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).
-:::
+FV can be used to calculate future value over a specified number of compounding periods. A fixed interest rate or yield is assumed over all periods, and a fixed payment or deposit can be applied at the start or end of every period.
+
+If your interest rate varies between periods, use the [FVSCHEDULE](./FVSCHEDULE) function instead of FV.
+## Usage
+### Syntax
+**FV(rate, nper, pmt, pv, type)**
+### Argument descriptions
+* *rate*. The fixed percentage interest rate or yield per period.
+* *nper*. The number of compounding periods to be taken into account. While this will often be an integer, non-integer values are accepted and processed.
+* *pmt*. The fixed amount paid or deposited each compounding period.
+* *pv* (optional). The present value or starting amount of the asset (default 0).
+* *type* (optional). A logical value indicating whether the payment due dates are at the end (0) of the compounding periods or at the beginning (any non-zero value). The default is 0 when omitted.
+### Additional guidance
+* Make sure that the *rate* argument specifies the interest rate or yield applicable to the compounding period, based on the value chosen for *nper*.
+* The *pmt* and *pv* arguments should be expressed in the same currency unit. The value returned is expressed in the same currency unit.
+* To ensure a worthwhile result, one of the *pmt* and *pv* arguments should be non-zero.
+* The setting of the *type* argument only affects the calculation for non-zero values of the *pmt* argument.
+<!--@include: ../markdown-snippets/error-type-details.md-->
+
+## Details
+* If *rate* = 0, FV solves the equation:
+$$
+FV = -pv - (pmt \times nper)
+$$
+
+* If *rate* <> 0 and *type* = 0, FV solves the equation:
+$$ FV = -pv \times (1 + rate)^{nper} - \dfrac{pmt\times\big({(1+rate)^{nper}-1}\big)}{rate}
+$$
+* If *rate* <> 0 and *type* <> 0, FV solves the equation:
+$$ FV = -pv \times (1 + rate)^{nper} - \dfrac{pmt\times\big({(1+rate)^{nper}-1}\big) \times(1+rate)}{rate}
+$$
+## Examples
+[See this example in IronCalc](https://app.ironcalc.com/?example=fv).
+
+## Links
+* For more information about the concept of "future value" in finance, visit Wikipedia's [Future value](https://en.wikipedia.org/wiki/Future_value) page.
+* See also IronCalc's [NPER](./NPER), [PMT](./PMT), [PV](./PV) and [RATE](./RATE) functions.
+* Visit Microsoft Excel's [FV function](https://support.microsoft.com/en-gb/office/fv-function-2eef9f44-a084-4c61-bdd8-4fe4bb1b71b3) page.
+* Both [Google Sheets](https://support.google.com/docs/answer/3093224) and [LibreOffice Calc](https://wiki.documentfoundation.org/Documentation/Calc_Functions/FV) provide versions of the FV function.

docs/src/functions/markdown-snippets/error-type-details.md

@@ -0,0 +1 @@
+* For information about the different types of errors that you may encounter when using IronCalc functions, visit our [Error Types](/features/error-types) page.