Assertion: ellipse's distance | /r/CapableOf | talk about $r_1$
Facets:
value: as a function of the angle
type: OTHER
Source sentences:
text: The distance of the earth from the sun (positioned at $F_1$, so we are talking about $r_1$) as a function of the angle $\phi$ is given by: \[ r_1(\phi) = \frac{a(1-\epsilon^2)}{1 - \epsilon\cos(\phi)}. \]