This has to be one of my favorite discovery lessons for my trigonometry students! With only right-triangle trigonometry (SOHCAHTOA) and some good algebra skills, my trigonometry students successfully derive the following formulas:
cos(a+b)=cos(a)cos(b) - sin(a)sin(b)
sin(a+b) = cos(a)sin(b) + sin(a)cos(b)
tan(a+b) = [tan(a)+tan(b)]/[1-tan(a)tan(b)]
This worksheet will "hold their hands" as they go through the process.
I use it within cooperative groups, and I circulate to make sure they are getting the purpose of the questions.
The file includes spiral review problems.
This worksheet is intended to be written on directly.
Please download the pdf preview file first, so you can see what's included; the product file is a word document, which you may personalize for your students.
NOTE: I have not included the answer key in the preview, but it's included in the word file. I sell a related product, listed right next to this one, which does not include the key, but has a lower price.
Keywords: composite argument formulas, sine of a sum, cosine of a sum, tangent of a sum, trigonometry, discovery, Jonnard