Lesson Plan: Three-by-Three Determinants Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to evaluate 3 × 3 determinants using the cofactor expansion (the Laplace expansion) or the rule of Sarrus.


Students will be able to

  • define minors and cofactors in a matrix,
  • use the cofactors method (Laplace expansion) to evaluate a 3×3 determinant,
  • use the Sarrus method to evaluate a 3×3 determinant.


Students should already be familiar with

  • 2×2 determinants.


Students will not cover

  • determinants of 4×4 and higher-dimensional matrices,
  • properties of determinants.

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