On progressions of arcs of circles, of which the accompanying tangents proceed by a certain law
According to Jacobi, a treatise with this title was read to the Berlin Academy on November 23, 1758. According to St. Petersburg Academy records, it was presented to that Academy on October 15, 1759.
Euler converts arctangents of reciprocals of quadratics into continued fractions and then gets some angles as continued fractions of quadratics. Faber says this is related to E74.
Original Source Citation
Novi Commentarii academiae scientiarum Petropolitanae, Volume 9, pp. 40-52.
Opera Omnia Citation
Series 1, Volume 15, pp.16-30.