The Calculator has several parts: a keypad, an input area, a preview area, and popup menus for inserting special mathematical elements
Click the buttons in the Calculator’s keypad to insert numbers, decimal points, operators, and parentheses into your calculation or function. Instead of clicking one of these buttons, you can type the corresponding key on your computer’s keyboard. (Use the / key — the forward slash — on the keyboard for division.) Click the leftarrow key on the keypad, or the Backspace key (Windows) or Delete key (Macintosh) on the keyboard, to delete the last item you typed. If you’re using the Calculator to define a function, you can click the key labeled x to enter the value of the independent variable. The x key is present only when you’re defining a function; it changes to y, θ, or r depending on the form of the equation. 
The input area displays each element you insert into the calculation or function as you enter it. Refer to the input area to see exactly what you’ve entered. You can also click in the input area or press the right or leftarrow key on the keyboard to change the insertion point and add new numbers, operators, and so forth in the middle of an existing expression. If the input area does not form a valid mathematical expression, the portion of the input area up to the first error is shown in black. The portion following the first error appears in red. 
The preview area shows a mathematically formatted preview of the input area when it contains a valid expression. Use the preview to be sure that you’ve entered the desired calculation or function correctly — that you have the parentheses in the right places and that you have the correct order of operations. 
Depending on whether you’re defining a calculation or a function, either three or four popup menus appear. The last of these, the Equation popup menu, appears only when you’re defining or editing a function rather than a calculation. You can click an existing value or function in the sketch to insert it into the Calculator. You can also click a Hot Text link to a value or function to enter it.

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