Creating a Custom Equation
- 
                Click the Equation tool 
 in the Design tab.
             - 
                (Optional) Click the Set Grid Location tool guide 
 and select a different sketch plane.
             - Choose Custom in the Curve Types drop-down list in the Options panel.
 - Enter the equation in the input panels.
 - To create a Parameter to use in the equation enter it in square brackets "
[ ]"- For example: 
[L] - The parameter is added to the Parameters list in the Options panel
 
 - For example: 
 - Click Complete to create the equation curve.