The solution to a geometric problem about circles shaped as moons
In this paper, Euler presents his solution, invovling the arcsine function, to a problem of Daniel Bernoulli (which Euler had heard about through Goldbach). The problem is related to dissecting certain circles into pieces, all of which have equal area.
Original Source Citation
Commentarii academiae scientiarum Petropolitanae, Volume 9, pp. 207-221.
Opera Omnia Citation
Series 1, Volume 26, pp.1-14.