PreCalculus - Trigonometry: The Right Triangle (25 of 26) Circumference of the Planet = ?

In this video I will find the circumference of a distant planet with an orbiting Earth satellite.

[rgulamhussein]

Thank you professor Van Biezen! I've learned so much from your lessons.
Please can you tell me the name of the Greek astronomer that you mentioned? I didn't quite catch the name.

[ahmedal-ebrashy]

In this case can I say sin 40 = arc length/ radius of planet because angle is very small?

[akiyoisreal]

I'm confused about the degree becoming 40° aswell.