This is the ninth in a series of major topics in trigonometry, adapted from lessons that I wrote for homeschoolers. It includes the sum and difference formulas and the multiple angle formulas. It shows how to use the formulas in verifying identities and solving equations. (There is an optional section on some more advanced formulas and their use in calculus.)The content is very organized and focused with many step-by-step examples and problems. This can be 4 or 5 lessons depending on available time. Download the preview to see suggestions and complete content for this product.