Physics Problem: Total Internal Reflection

A light ray entering an optical fiber surrounded by air is first refracted and then reflected as shown in Figure 25.54. Show that if the fiber is made from crown glass, any incident ray will be totally internally reflected.
I'm working through chapter summaries for introductory physics (algebra-based). I'm using the Openstax online (free) textbook College Physics. You can access this book here openstax.org/d...
Here is the playlist with all the videos and problems for this course.
• Online Physics 2 2024

[@fizixx]

Kewl. I don't think there's a trig identity for that, but no matter. It's all good. :)