Functions of Three Real Variables is a mathematical textbook written by Henry Livingston Coar and first published in 1906. The book provides a comprehensive treatment of functions of three variables, including topics such as limits, continuity, partial derivatives, multiple integrals, and vector calculus. The book is intended for advanced undergraduate or graduate students in mathematics, physics, or engineering who have a solid foundation in calculus and linear algebra. Throughout the book, Coar emphasizes the importance of visualization and geometric intuition in understanding the behavior of functions of three variables. The book includes numerous examples, exercises, and solutions to selected problems, making it a valuable resource for students and instructors alike. Despite its age, Functions of Three Real Variables remains a classic text in the field of multivariable calculus and is still widely used today.This scarce antiquarian book is a facsimile reprint of the old original and may contain some imperfections such as library marks and notations. Because we believe this work is culturally important, we have made it available as part of our commitment for protecting, preserving, and promoting the world's literature in affordable, high quality, modern editions, that are true to their original work.