To enter the equation editor, click on the Insert tab and select the equation button on the far right. 
This brings up the Equation Tools ribbon with many preset symbols and options. 
The equation is entered in the highlighted text box on the worksheet.
Mathematicians, have fun!
For larger spreadsheets, Range Names are more convenient than scroll bars. To name an individual cell or block of cells highlight the cell or cells first, click on the Name Box, type in an appropriate name, and press the Enter key. (Range names do not accept spaces.)
To find the block again, use the drop-down list in the Name Box and click on the name. Alternatively use the GoTo command (Ctrl+G or F5). Note: Range names can also be used in formulae instead of their cell reference equivalent.
To edit or delete range names, use the Name Manager from the Formulas tab. Note that the delete option only deletes the range name, and not the contents of the cells in that range.