""A Key to the Exercises in the First Six Books of Casey's Elements of Euclid"" is a book written by Joseph B. Casey and published in 1885. The book serves as a guide for students who are studying Euclidean geometry using Casey's textbook ""Elements of Euclid."" It contains solutions and explanations for the exercises found in the first six books of the textbook, which cover topics such as lines, angles, triangles, circles, and proportions. The book...