Polar equation

1. Nov 15, 2006

merced

I have the given polar equation that I have to graph.

r = 5/(-1 + 2 cos θ)

The format is r = ed/(1 +e cosθ)

(e and d are always positive)

I can solve multiply r by -1/-1 --> r = -5/(1 - 2 cosθ).

Is this possible? I thought that the numerator (ed) cannot be a negative number. Is this a misprint or is there a way to solve this?

2. Nov 15, 2006

TMFKAN64

r can be negative... it just means that you actually go 180 degrees the other direction. So for example, when theta is 180 degrees, r is -5/3... so the point is at 5/3 on the *positive* x-axis.