Windstream
Ojk's Precalculus Study Page: Sum and Difference Formulas for Tangent
This tutorial introduces the sum and differnce formulas for tangent, and gives several examples of problems to be solved as well as proving other identities. Assumes knowledge of the sum and difference formulas for sine and cosine.
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Sum and Difference Formulas
Twenty problems are presented for practice working with sum and difference formulas for sine, cosine, and tangent.
Analyze Math
Analyze Math: Trigonometry: Sum and Difference Formulas
Students explore trigonometric formulas. Definitions of the sum and difference formulas are included.