Paul's Online Notes
Home / Calculus II / Parametric Equations and Polar Coordinates / Parametric Equations and Curves
Show Mobile Notice Show All Notes Hide All Notes
Mobile Notice
You appear to be on a device with a "narrow" screen width (i.e. you are probably on a mobile phone). Due to the nature of the mathematics on this site it is best views in landscape mode. If your device is not in landscape mode many of the equations will run off the side of your device (should be able to scroll to see them) and some of the menu items will be cut off due to the narrow screen width.

### Section 3-1 : Parametric Equations and Curves

For problems 1 – 6 eliminate the parameter for the given set of parametric equations, sketch the graph of the parametric curve and give any limits that might exist on $$x$$ and $$y$$.

1. $$x = 4 - 2t\hspace{0.5in}y = 3 + 6t - 4{t^2}$$ Solution
2. $$x = 4 - 2t\hspace{0.5in}y = 3 + 6t - 4{t^2}\hspace{0.5in}0 \le t \le 3$$ Solution
3. $$\displaystyle x = \sqrt {t + 1} \hspace{0.5in}y = \frac{1}{{t + 1}} \hspace{0.5in} t > - 1$$ Solution
4. $$x = 3\sin \left( t \right)\hspace{0.5in}y = - 4\cos \left( t \right) \hspace{0.5in} 0 \le t \le 2\pi$$ Solution
5. $$x = 3\sin \left( {2t} \right)\hspace{0.5in}y = - 4\cos \left( {2t} \right) \hspace{0.5in}0 \le t \le 2\pi$$ Solution
6. $$\displaystyle x = 3\sin \left( {\frac{1}{3}t} \right)\hspace{0.5in}y = - 4\cos \left( {\frac{1}{3}t} \right) \hspace{0.5in}0 \le t \le 2\pi$$ Solution

For problems 7 – 11 the path of a particle is given by the set of parametric equations. Completely describe the path of the particle. To completely describe the path of the particle you will need to provide the following information.

1. A sketch of the parametric curve (including direction of motion) based on the equation you get by eliminating the parameter.
2. Limits on $$x$$ and $$y$$.
3. A range of $$t$$’s for a single trace of the parametric curve.
4. The number of traces of the curve the particle makes if an overall range of $$t$$’s is provided in the problem.

1. $$x = 3 - 2\cos \left( {3t} \right)\hspace{0.5in}y = 1 + 4\sin \left( {3t} \right)$$ Solution
2. $$x = 4\sin \left( {\frac{1}{4}t} \right)\hspace{0.5in}y = 1 - 2{\cos ^2}\left( {\frac{1}{4}t} \right) \hspace{0.5in} - 52\pi \le t \le 34\pi$$ Solution
3. $$\displaystyle x = \sqrt {4 + \cos \left( {\frac{5}{2}t} \right)} \hspace{0.5in}y = 1 + \frac{1}{3}\cos \left( {\frac{5}{2}t} \right) \hspace{0.5in} - 48\pi \le t \le 2\pi$$ Solution
4. $$\displaystyle x = 2{{\bf{e}}^t}\hspace{0.5in}y = \cos \left( {1 + {{\bf{e}}^{3t}}} \right) \hspace{0.5in} 0 \le t \le \frac{3}{4}$$ Solution
5. $$\displaystyle x = \frac{1}{2}{{\bf{e}}^{ - 3t}}\hspace{0.5in}y = {{\bf{e}}^{ - 6t}} + 2{{\bf{e}}^{ - 3t}} - 8$$ Solution

For problems 12 – 14 write down a set of parametric equations for the given equation that meets the given extra conditions (if any).

1. $$y = 3{x^2} - \ln \left( {4x + 2} \right)$$ Solution
2. $${x^2} + {y^2} = 36$$ and the parametric curve resulting from the parametric equations should be at $$\left( {6,0} \right)$$ when $$t = 0$$ and the curve should have a counter clockwise rotation. Solution
3. $$\displaystyle \frac{{{x^2}}}{4} + \frac{{{y^2}}}{{49}} = 1$$ and the parametric curve resulting from the parametric equations should be at $$\left( {0, - 7} \right)$$ when $$t = 0$$ and the curve should have a clockwise rotation. Solution