Two Remarkable Identities, Called Twos, for Inverses to Some Abelian Integrals

Remark. The reason for this strange terminology is that in the Swedish educational system the first of the aforementioned formulae is, at least informally, referred to as the trigonometric One ("trigonometriska Ettan"); more recently, we learnt from various colleagues that a similar terminology is used in other European countries as well, for instance, Poland and the Czech Republic. For example, for certain functions called sinualis and cosinualis and denoted Sm and Cm, Erik Lundberg [6] proved, in 1879, the notable formula p p