How to enter a formula into a custom field formatted as a formula

To enter a formula into a custom field formatted as a formula:           

1. Formulas can contain the following math operators:  *  /  +  -  (  )                                   
2. To reference an Other Information field in your formula, surround it with square brackets. Example of a tax calculation:  [Amount] * 0.15                                   
3. Additional functions are:                                           
• SQRT(expression): Calculates square root of expression                                           
• POWER(expression, y): Raises expression to the power of y
• ROUND(expression, x): Rounds expression to x digits after decimal                                           
• ABS(expression): Calculates absolute value of expression
• Note: expression denotes either a value, a reference to a field or any calculation on such                        
4. Formula Example:  ( [Amount] - ( [Amount] * [Discount] ) ) * 1.15
                                           
• The above formula makes a Total calculation by applying a discount contained in another field and adds taxes of 15%.