Editing True anomaly (section)

===Radius from true anomaly===
The radius (distance between the focus of attraction and the orbiting body) is related to the true anomaly by the formula

:<math>r(t) = a\,{1 - e^2 \over 1 + e \cos\nu(t)}\,\!</math>

where ''a'' is the orbit's [[semi-major axis]].

In [[celestial mechanics]], '''Projective anomaly''' is an angular [[parameter]] that defines the position of a body moving along a [[Keplerian orbit]].  It is the angle between the direction of [[periapsis]] and the current position of the body in the projective space.

The projective anomaly is usually denoted by the <math>\theta</math> and is usually restricted to the range 0 - 360 degree (0 - 2 <math>\pi</math> radian).

The projective anomaly <math>\theta</math> is one of four angular parameters (''anomalies'') that defines a position along an orbit, the other two being the [[eccentric anomaly]],  [[true anomaly]] and the [[mean anomaly]].

In the projective geometry, circle, ellipse, parabolla, hyperbolla are treated as a same kind of quadratic curves.