EULER, Leonhard. De insigni promotione methodi tangentium inversae; Demonstratio theorematis Bernoulliani quod ex evolutione curvae cuiuscinque rectangulae in infinitum continuata tandem cycloides naxcantur; Nova criteria radices aequationum imaginarias discoscendi.
St. Petersburg : Typis Academiae Scientiarum, 1766-1769. All first editions.

Extracted from: Novi Commentarii Academiae Scientiarum Petropolitanae, Vol. 10, pp. 135-155 and 1 plate; pp. 179-198 and 1 plate; Vol. 13, pp. 89-119. 4to: 265x206 mm. Contemporary bound in three. Blue paper boards with handwritten paper labels to front baord. Spine strips with some wear. Internally fine. Uncut and mostly unopened. Eneström: E298: (On the notable advancement of the inverse method of tangents); E300: (Demonstration of a Bernoullian theorem in which cycloids are ultimately produced from the evolution, continued to infinity, of any right-angled curve); E370: (A new criteria for acquiring the imaginary roots of equations).