I figured anyone who could read mathematical notation would know enough to do the math themselves and so wouldn't need the tutorial. It really is just the most basic of trig.

∆y = r ∆φ
∆x(φ) = r ∆λ cos φ

Where r is the radius of the planet, ∆φ is the angular spacing of the parallels of latitude, ∆λ is the angular spacing of the meridians of longitude, ∆y is the linear spacing of the parallels of latitude, and ∆x(φ) is the linear spacing of the meridians of longitude at a latitude of φ, with all angles expressed in radians.