Update README.md

added documentation.

README.md

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 # vue-calculator
+## Documentation
+### Features
+#### Multiple-Calculations
+In this app, you can have infinite lines of calculations, similar to a graphics calculator. To create a new line/calculation, press the enter key, and a new line will be added below the currently selected line.
+
+#### Copying Answers To Clipboard
+To copy a result froma calculation to the clipboard, simply click the result, and it will be copied to the clipboard to be pasted later.
+You can also type "ans" to reference the answer to the previous calculation.
+
+#### Powers
+To use powers in your calculations, use the "^" symbol to write in super script. Then to end the power type ";", and the cursor will drop back down to the lower level. For example, if I wanted to calculate 5 squared, I would type "5^2;". This application also supports nested powers, for example, if I wanted to calculate 5 to the power of 5 squared, I would type "5^(5^2;);".
+
+### Functions
+Vue-calculator supports many functions, each of which is listed below.
+ - sin(angle)
+ - cos(angle)
+ - tan(angle)
+ - log() base 10
+ - ln()
+ - sec(angle)
+ - cosec(angle), csc(angle)
+ - cot(angle)
+
+### Constants
+Currently the only constant supported is pi. If you type in "pi", it automatically gets replaced with the symbol for pi. I plan to add euler's constant.
+
+### Comments
+If you want to add some descriptions to your calculations, start a new line with "//" and the app will not attempt to calculate that line, so you can write a description without worrying about errors.
+
+### Settings
+To open settings, click the cog icon in the top right corner, and a panel will slide out. To close the settings, click the cog again.
+#### Angle Mode
+The following angle units are supported:
+- degrees
+- radians
+- gradians
+To switch between them, open the settings. Click on the text that displays what unit is currently being used, and it will cycle between the units.
+
+#### Precision
+To change the number of significant figures that results are rounded to, enter the number of significant figures into the input field in settings, corresponding to "Precision".
 
 ## Project setup
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