I really like the simplicity of this One or Negative One? Trig Identities Task that I found in the 8th Edition of Demana and Waits’ Pre-Calculus Textbook (Section 5.1). That’s why I decided to turn it into a worksheet!
Trig identities are one of my favorite topics to teach in Pre-Calculus. To me, they are a puzzle, and I try to present them to students as a puzzle.
In this activity, students are given five trigonometric expressions. Using trig identities, each expression can be simplified to either 1 or -1. Often when I teach students to simplify trigonometric expressions, they struggle to know when the expression is simplified “enough.” I like this activity since they have a target to aim for (1 or -1), but I haven’t told them the exact target like I do when we prove trig identities.
I did have a few students who just wanted to randomly write down 1 or -1 for each problem… They were a bit annoyed when I told them they had to justify their answers!
You might also be interested in my Verifying Trig Identities Worksheet and Trig Identities Matching Activity.
Free Download of One or Negative One Trig Identities Worksheet
One or Negative One Trig Identities Task (PDF) (453 downloads)
One or Negative One Trig Identities Task (WORD) (203 downloads)