I was still very tired for most of today, but I rallied in the late afternoon and managed to do 90 minutes of trig review and 30 of investigation into the parabola problem. I think I’m making progress, though I haven’t started trying to work out all the algebra and trig yet.
I will probably need some inverse trigonometric identities. I was not certain such things existed, but apparently they do. Most of the exercises I did today concerned the regular kind: either proving them or using them to turn one expression into another. I remember doing a lot of the latter kind of problem in my tenth-grade precalculus class. I always thought they were kind of fun.