Friday, May 16, 2014

10.5 Parametric Equations

Definition of a plane curve

If f and g are continuous functions of t on an interval l, the set of ordered pairs (f(t),g(t)) is a plane curve C. The equations:

 

        x=f(t)      and     y=g(t)

are parametric equations for C, and t is the parameter.

 

Eliminating the Parameter

1. Parametric equations

2. solve for t in one equation

3. substitute into second equation

4.rectangular equation (only 2 variable)

 

Example:

1.
x=t+3, y= -t^2

step 1:  subtract both side of x=t+3 by three:

                                x-3=t

then, take x-3 into another equation

                   get   y= - (x-3)^2

 


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