If you move the cursor to the top of the Y1 column, the equation that we used to define Y1 in the function editor will appear at the bottom of the screen. This is convenient if you have forgotten what the function was, or if you want to change the function. For example, let's change the function from sine to cosine. Once the equation appears, you can edit this line. In this case, all you need to do is press the COS key.