1.4 Parametric Equations Mt. Washington Cog Railway, NH Greg Kelly, Hanford High School, Richland, Washington Photo by Greg Kelly, 2005
There are times when we need to describe motion (or a curve) that is not a function. We can do this by writing equations for the x and y coordinates in terms of a third variable (usually t or ). These are called parametric equations. “t” is the parameter. (It is also the independent variable)
To graph on the TI-89: Graph……. 2 Y= WINDOW GRAPH Example 1: T ) MODE ENTER PARAMETRIC Y= 2nd T ) ENTER WINDOW GRAPH
Hit zoom square to see the correct, undistorted curve. We can confirm this algebraically: parabolic function
Circle: If we let t = the angle, then: Since: We could identify the parametric equations as a circle.
Graph on your calculator: Use a [-4,4] x [-2,2] window. WINDOW GRAPH
Ellipse: This is the equation of an ellipse. p