# I Orbit invariant under reflection about apsidal vectors

1. Mar 21, 2016

### Happiness

The book argues that since substituting $\theta$ by $-\theta$ leaves the orbit equation (3.34) unchanged, the orbit is therefore invariant under reflection about the apsidal vectors (Fig 3.12).

If substituting $\theta$ by $-\theta$ leaves the orbit equation (3.34) unchanged, then there exists a plane of symmetry (where $\theta=0$) in the orbit. How does the book reach the conclusion of invariance under reflection about the apsidal vectors?

2. Mar 26, 2016

### Greg Bernhardt

Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?