> 2500 miles * 2500 miles * pi = 19,630,000 miles squared > So that area represents about (19.63 / 57.51 ) 34% of the total world landmass. So 50% of humans li

> 2500 miles * 2500 miles * pi = 19,630,000 miles squared > So that area represents about (19.63 / 57.51 ) 34% of the total world landmass. So 50% of humans live in 34% of the landmass. I've been telling myself that I have to teach myself Non-Eucledian Geometry, but lacking any real motivation, I've successfully procrastinated for 6 years. The unfortunate itch to be pedantic on the internet will hopefully drive me to learn how to correctly calculate the area of a circle on a sphere. Anybody has a good textbook recommendation?