Free Calculus Textbooks

By Xah Lee. Date:
By Xah Lee. Date: . Last updated: .
Integral approximations
Integral approximation. [ image source 2016-05-12 ]

Here is a collection of calculus textbooks. These are top quality, and legally free.

APEX Calculus by Gregory Hartman et al

Calculus Volume 1. OpenStax project

Calculus, by Jim Fowler, Bart Snapp