Mathematics (AS)·Trigonometry · NSSCAS 2.3.3
Double angle formulae
Narrated lesson · press play
In this lesson you'll learn the double angle formulae for sin 2A, cos 2A and tan 2A, and see exactly where each one comes from. You'll master the key exam skill of choosing the right form of cos 2A. You'll find exact values from a right triangle, prove an identity, simplify expressions, and solve equations — all without ever losing a solution.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Mathematics (AS) 2.3.3):
- Use the formulae for sin 2A, cos 2A (all three forms) and tan 2A, deriving each from the compound angle formulae.
- Use double angle identities for simplification, exact evaluation, proving identities, and solving trigonometric equations, selecting the appropriate identity each time.
Loading your lesson…
You're watching a free 3-minute preview — create a free account to keep going.