# More than One Parameter Here are the two Haskell functions used in the Getting Started section: ```haskell areaCircle x = 3.14 * x areaSquare x = x * x ``` Note that Haskell functions must start with lower case letters. Remember, whilst you are learning you can type up functions in your favourite editor and then load them into the editor using :l path/to/file. Use :r to reload the functions when you've made changes to them. Here's how to write functions with two parameters: ```haskell areaRectangle l w = l*w perimeterRectangle l w = 2*l + 2*w ``` # Partial Application AQA defines partial application as the process of applying a function by creating an intermediate function by fixing some of the arguments to the function As and example, lets consider the areaRectangle function above. Suppose you want to work out the areas of all rectangles where one side is fixed at 3. You can write a function, area3Rect, as follows ```haskell area3Rect = areaRectangle 3 ``` You can now work out the areas of different rectangles as follows ```haskell *Main> area3Rect 4 12 *Main> area3Rect 5 15 *Main> area3Rect 6 18 *Main> ``` area3Rect is a partially applied function - a function where some of the parameters have been fixed. Try creating a partially applied function based on perimeterRectangle. This leads us nicely on to Higher Order Functions… # Next - [[Higher Order Functions]]