Chapter 30
It is true that in this way (that is, in associating the distance αζ of the angle δαζ with an angle which is as much smaller than δαζ as δαζ is smaller than (δβζ) a path is attached to the circuit of the earth (or sun) about α which is oval rather than exactly circular.
(pp. 363-364)
The blue point traces out this proposed oval (non-elliptical) path of the planet along the dashed green line.
Here, three lines come out of the sun at α:
- δβζ is not connected to anything
- δαζ is connected to the red point on the circle
- the third line is connected to the blue location of the planet on the oval path.
The differences between these angles are the same. Further, the length from the sun to the red point is the same as the length from the sun to the blue point.