Where is the vertical directrix of a conic if the denominator of its polar equation has the form 1-e cosq?

1 Answer
vince
Feb 18, 2015

Hello !

You need the numerator.

If the polar equation of your conic is r = \frac{p}{1 + e\cos(\theta)}, both directrix are vertical and one of them contains the point P(\frac{p}{e},0).

If the denominator is 1-e\cos(\theta), write :

1-e\cos(\theta) = 1 + e\cos(\theta - \pi).

Both directrix are vertical and one of them contains the point P(-\frac{p}{e},0).

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