You can use symbolic variables to constrain geometry with an implicit equation. Lines, line segments, polygon sides, vectors and circles can all be constrained with implicit equations.
| 1. | Select  the geometry. |
| 2. | Click the Implicit Equation icon  from the Constrain toolbox, or select Implicit Equation from the Constrain menu. |
An input window will open next to the geometry you selected. Highlighted in the window is a generic equation for the selected object; for a line, an equation like - XA1+YB1+C1 = 0 might appear. You can edit the equation with different variable names or coefficients as you like. You will find these variables added to the variable list in the Variables toolbox.