These web pages are provided to help high school and college/university students eliminate common trigonometry mistakes. The approach here is not to give a list of the types of those mistakes (see some of the links on the "Other Web Resources" page for such lists), but instead to show examples of such mistakes along with corrections and brief explanations. My hope is that these examples complement what your teachers and texts tell you about correct methods for solving trigonometry problems, and that they will help you eliminate these kinds of mistakes.

Over a period of many years teaching (more years than I care to reveal here) I have seen far too many algebra and trigonometry mistakes, both careless and from mislearned and misunderstood application of techniques. These mistakes have prevented students from arriving at the correct solutions to problems they clearly understand how to solve at a conceptual level. For some time I have thought about how to share examples of various common types of mistakes that pervade student work from beginning algebra through to upper division math courses. Many years ago I envisioned recording these mistakes and then distributing them back to students in a Bad Algebra Digest (aka "B.A.D.", a delightfully recursive title). I never did. Now, here on these pages, is a collection (that will undoubtably grow) of mistakes of the sort that should not occur. Such a collection can never be complete, for there are endless variations on the mistakes that can be made.

• If you are a student who makes more algebra and trigonometry mistakes than you would like, look through the examples. Try to find the mistakes before checking the corrections. Read through the explanations. If something does not make sense, write to me at the email address below.
• If you have suggestions for improving these pages, you may send them to the email address below. I don't guarantee to use any suggestions or material sent to me. Please note: If you send me any material, you agree that I will provide you no compensation or sharing of any revenue generated by the web site in exchange for using that material.
• If you notice any serious errors on these web pages, I would appreciate hearing from you so that I may correct the problem. Please realize that reasonable people will disagree about how to explain certain mistakes or concepts. In certain cases, therefore, I may not act on your advice. I may in certain cases receive or have a conflicting opinion on some aspects of these pages and will choose the approach that makes the most sense to me. Therefore, please resist the temptation to nit-pick the content of these pages.

Email address: comments [at] mathmistakes [dot] info