Before revision: 1, φ is the latitude , positive northward, and λ is the longitude , positive eastward), the initial and final courses α1 and α2 are given by formulas for solving a spherical triangle where λ12 = λ2 − λ1In the article on great-circle distances, the notation Δλ = λ12 and Δσ = σ12 is used.
After revision: 1, φ is the longitude , positive northward, and λ is the latitude , positive eastward), the initial and final courses α1 and α2 are given by formulas for solving a spherical triangle where λ12 = λ2 − λ1In the article on great-circle distances, the notation Δλ = λ12 and Δσ = σ12 is used.