University of California
University of California, Davis: The Calculus Page
This site, from the University of California, provides several problems from beginning differential calculus, as well as beginning integral calculus. The problems can be accessed by clicking on the link, and the information provided is...
CK-12 Foundation
Ck 12: Algebra Ii: 4.8 Pythagorean Identities
This section explores the Pythagorean Identity and how it applies to right triangles set inside unit circles, in terms of sine, cosine, and tangent functions.