PreCalc · Unit 9

Sum & Difference Formulas

sin(a±b), cos(a±b)

Curriculum standard — Generalize stage of the Thinking Ladder

AMC 8

This concept — appears in non-routine form on competition pathways, where the same structure is disguised in an unfamiliar setting.

A competition problem that uses this concept's structure in a way standard practice does not surface.

Procedural fluency→Structural generalization

Challenge problems ask you to generalize — what stays true when the numbers or context change?

Three pathways, one topic

Study sum & difference formulas at three depths

Grade/course-level problems with full understanding.

Parameters, multiple representations, proof, and modeling.

Non-routine problems and competition applications.