Trigonometric Identities
Main Concepts
Matrix multiplication
Rotation matrix in the plane
Trigonometric identities
Duration
20 minutes
Summary of Activity
The sum and difference formulas for trigonometric functions can be elegantly proven using rotation matrices and some matrix multiplication. Matrix multiplication is defined to correspond to the composition of the two transformations.
Notes and Insights
This task can also be handed out to students in Precalculus, even though their understanding of matrix multiplication is mostly computational.