Questions from Teresa,
I’m in Jacobs Geometry, Chapter 14, Lesson 2. The answer to problem 16 is 9 sin 20 degrees. How do you get that answer?
First, from #15 you see we count 9 sides. So, n=9.
For #16, based on the formula from Theorem 75 on page 581
N = nsin(180/n)
we just plug in the 9 to get
N = 9sin(180/9) = 9sin20.