Okay so next up is the Gudermannian function which…en.wikipedia.org/wiki/Guderman… “relates circular functions and hyperbolic functions without complex numbers”

the image here relates to the part about…well I’ll translate for you;The Gudermannian of the latitudinal distance from the equator on a “Mercator projection” ( a map rolled flat) is the “meridian arc length” (accurate determination of distance between two points with the same longitude of a “Geoid”—the shape the oceans would make if gravity alone was influencing them) of the actual latitude on the globe

in other words this can be used to measure the earth—I’m assuming…what fun =3