Addition Formulae
Overview
How do you find the exact value of sin 75 degrees without a calculator? The answer lies in rewriting 75 as a sum of angles whose trigonometric values you already know. Addition formulae let you break compound angles into manageable pieces, opening the door to exact calculations, identity proofs, and equation solving that would otherwise be impossible.
In this topic you will master the six addition formulae for sine, cosine and tangent, then derive the powerful double angle identities that follow directly from them. These results appear in almost every Further Pure trigonometry question, so fluency here pays dividends across the entire paper.
Objectives
- Use the addition formulae for sin(A + B), cos(A + B) and tan(A + B)
- Use the addition formulae for sin(A - B), cos(A - B) and tan(A - B)
Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Addition Formulae. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which of the following is the correct expansion of sin(A + B)? A) sin A sin B + cos A cos B B) sin A cos B + cos A sin B C) sin A cos B - cos A sin B D) cos A cos B - sin A sin B Answer: B
- What is the value of cos 2A when expressed using only cos A? A) 2 cos A - 1 B) 2 cos squared A - 1 C) 1 - 2 cos squared A D) cos squared A + 1 Answer: B
- Given that tan A = 3 and tan B = 2, what is tan(A + B)? A) 5 B) -1 C) 1 D) -5 Answer: B (using tan(A+B) = (3+2)/(1-6) = 5/(-5) = -1)
- Sin 2A is equivalent to: A) 2 sin A B) sin A cos A C) 2 sin A cos A D) sin squared A + cos squared A Answer: C
- The expression (1 - cos 2x) / 2 simplifies to: A) cos squared x B) sin squared x C) tan squared x D) 1 Answer: B
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Practice Mock Questions
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