Mathematics (AS)·Trigonometry · NSSCAS 2.3.2
Compound angle formulae
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In this lesson you will learn the six compound angle formulae for sine, cosine and tangent, and how to USE them even though they are printed in the exam formula list. You will find exact values like sin 75° and cos 15° using surds, prove a small identity, and solve an equation by expanding a compound angle. By the end you will handle the tricky sign flip in cosine and tangent with total confidence.
What you'll learn in this lesson
By the end you should be able to (NSSCAS Mathematics (AS) 2.3.2):
- Use the expansions of sin(A ± B), cos(A ± B) and tan(A ± B).
- Use trigonometric identities for the simplification and exact evaluation of expressions, and in solving equations, selecting an appropriate identity for the context.
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