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# Polar Coordinates help watch

1. Hi guys,

Can someone explain why r=(1/1+2cosϴ) for -2/3Pi < ϴ , 2/3 Pidoes not have a pole? I was able to differentiate it so I'm quite confused. I got ϴ = 0

Thanks
2. (Original post by ChemBoy1)
Hi guys,

Can someone explain why r=(1/1+2cosϴ) for -2/3Pi < ϴ , 2/3 Pidoes not have a pole? I was able to differentiate it so I'm quite confused. I got ϴ = 0

Thanks
The pole is where and clearly the function is never 0
3. Thank you very much, I seem to having difficulties with this part of the topic. It said in the book that if F(Thetha) = 0 then the theta is tangent to the graph
(Original post by RDKGames)
The pole is where and clearly the function is never 0
4. Also if there was a situation with more than 1 trig function e..g. 2+ cos theta - cos^2 theta. How are you meant to find out the tangents to the pole?
5. (Original post by ChemBoy1)
Also if there was a situation with more than 1 trig function e..g. 2+ cos theta - cos^2 theta. How are you meant to find out the tangents to the pole?
Try to use the correct terminology. The pole is a point, so it wouldn't make sense to have something 'tangent' to it.

Here you are interested in straight lines going through the pole, which are tangent to your polar eq. . These lines have equation for (or between 0 and 2 pi, if you want to use that).
The first step is to obvious set and solve it for the values. But make sure that .
For the example above, we would simply need to solve but note that this is just a quadratic in which also factorises.

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Updated: February 8, 2018
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