Trigonometric proofs using De Moivre’s theorem

Specialist Mathematics · Unit 3 — Further complex numbers, proof, vectors and matrices · Mathematical induction and trigonometric proofs

Learning objectives (1)

LO-1Prove multi-angle trigonometric identities up to angles of 4𝑥 by equating parts using the binomial expansion and De Moivre’s theorem, e.g. cos(3𝑥) = 4 cos3(𝑥) − 3 cos(𝑥) and sin(3𝑥) = 3 sin(𝑥) − 4 sin3(𝑥). Specialist Mathematics 2025 v1.4

Practise these objectives with instant AI marking

Adaptive questions tied to QCAA mark schemes. Free to start.

Start free practice