# Textbooks of Lacroix: Elements of Algebra and Geometry

Author(s):
Frank J. Swetz (The Pennsylvania State University)

This is the title page of Lacroix’s Elements of Algebra, the ninth edition, 1811. The book was first published in 1800.

On page 13 of his Algebra, above, Lacroix discussed the construction of algebraic statements involving one variable, $x,$ and three constants, $a, b, c.$

This is the title page of Lacroix’s Elements of Geometry, sixth edition, 1810. The work first appeared in 1799.

On pages 78 and 79 of Lacroix's Geometry, above, Problems 124, 125, and 126 are posed. Each problem requires the construction of a circle under given conditions. A reader of French can appreciate the specific details of the explanations. Problems 124 and 126 can be understood by referring to Figures 70 and 64 in accompanying Plate IV.

Plate IV, above, illustrates various geometric situations involving circles that are considered in the text.

The images above are supplied through the courtesy of the Rare Books and Manuscript Collection of the Pennsylvania State University Library and the assistance of Dr. Sandra Stelts, Curator of the Collection.

##### Reference

J. J. O’Connor and E. F. Robertson, “Sylvestre François Lacroix (1765-1843),” MacTutor History of Mathematics Archive

Frank J. Swetz (The Pennsylvania State University), "Textbooks of Lacroix: Elements of Algebra and Geometry," Convergence (June 2015)