Southperry.net
(Polar Equations) Finding the equation of a ellipse and hyperbola - Printable Version

+- Southperry.net (https://www.southperry.net)
+-- Forum: Social (https://www.southperry.net/forumdisplay.php?fid=14)
+--- Forum: Rubik's Cube (https://www.southperry.net/forumdisplay.php?fid=58)
+--- Thread: (Polar Equations) Finding the equation of a ellipse and hyperbola (/showthread.php?tid=39830)



(Polar Equations) Finding the equation of a ellipse and hyperbola - Imagine - 2011-03-27

1. Given the vertices (2,0) and (10, pi), find the equation of the ellipse.
2. Given the vertices (1, 3pi/2) and (9, 3pi/2), find the equation of the hyperbola.
I seriously have no clue on what do to for these type of problems.


(Polar Equations) Finding the equation of a ellipse and hyperbola - Shidoshi - 2011-03-27

ellipsis should probably be something like this:

(sin(theta)/A)²+(cos(theta)/B)²=1/r²
With A and B being the maximum distance they go.

from the cartesian equation:
(x/A)²+(y/B)²=1


But I think with the vertices you should build the equations from the ellipsis definition:
"A cord of fixed length tied to the two vertices will pass by all points of an ellipsis when held stretched"


(Polar Equations) Finding the equation of a ellipse and hyperbola - 2147483647 - 2011-03-27

 Spoiler
-------

Edit: Crap. I didn't see that this is in polar form. That drastically simplifies things. For polar equation, the origin is always one of the focal points.

The general equation for a horizontal ellipse that has the center at π is:

r(θWink = a*(1-e^2)/(1+e*cos(θWink)

The general equation for a vertical hyperbola that has center at 3π/2 is:

r(θWink = a*(e^2-1)/(1+e*sin(θWink)

e is the eccentricity.

e = c/a

where c is the distance from the center of the conic to the focus
and a is the radius along the longer axis

This is the same a as the a in the equation.

Plug and chug. I wasted so much time doing it in rectangular. Lol.


(Polar Equations) Finding the equation of a ellipse and hyperbola - madanthony - 2011-03-28

If you want to take an hour or two and really learn it, I bet Khan can help.

http://www.khanacademy.org/video/introduction-to-conic-sections?playlist=Algebra
That's the starting point, and there are about 10 videos of relevance following that. If you make an account, there are exercises as well.