6.3  Graphing Para and Rect Eq Desmos

Graphing Parametric and Rectangular Equations in Desmos

Before you do these problems, make sure you review the process given in the Slide presentation - Slide #5.   

  Review the process using the resource document on the next two pages. (Two_Graphs_Desmos)

 NOTE: Some equations are impossible to rewrite in terms of x - i.e. x = y^2 - 3y + 2.

 This would be crazy to rewrite as y = ..., so leave equations like the above example as it is.

   It isn't difficult to see how parametric and rectangular equations are related.

   If we can change a parametric equation to a rectangular equation, then we should be able to see the graphs of both on one grid.

   We can graph the two equations on one grid using Desmos, but we will not be able to graph them on one grid using a graphing calculator.  Why?  (Think about this)

   For us to graph these equations in Desmos, we need to

           ~  Convert the parametric equation to a rectangular equation (either in terms of x or in terms of y).

           ~  Write the parametric equations as an ordered pair (x, y). Both x and y will be replaced by the parametric equations.

            ~  Know the domain for t for the parametric equation.