Trigonometric Ratios And Applications
Overview
SOHCAHTOA is powerful, but it only works inside a right-angled triangle. Surveyors, sailors and pilots rarely get one handed to them: they measure whatever angles and distances are convenient and need tools that work on any triangle at all, right-angled or not.
This topic extends trigonometry beyond 90 degrees, then builds the sine rule, the cosine rule and the area formula \(\frac{1}{2}ab\sin C\) for solving any triangle. It finishes with the three classic application types Edexcel tests hardest: angles of elevation and depression, bearings, and problems that step into three dimensions.
Objectives
- Use sine, cosine and tangent of angles up to 180 degrees
- Solve problems in two and three dimensions by calculation and by drawing, using the sine rule, cosine rule and the formula area = 1/2 ab sin C
- Understand and use angles of elevation and depression
- Understand and use bearings measured clockwise from north
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 Trigonometric Ratios And Applications. 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.
- What is the value of sin(150 degrees)? A) -0.5 B) 0.5 C) 0.866 D) -0.866 Answer: B
- Which rule should be used when three sides of a triangle are known and an angle is required? A) Sine rule B) Cosine rule C) SOHCAHTOA D) Area = 1/2 ab sin C Answer: B
- The angle of elevation from a boat to a lighthouse is 20 degrees. What is the angle of depression from the lighthouse to the boat? A) 20 degrees B) 70 degrees C) 90 degrees D) 160 degrees Answer: A
- A bearing of 128 degrees has a back bearing of: A) 052 degrees B) 232 degrees C) 308 degrees D) 128 degrees Answer: C
- In a right-angled triangle, when angle A = 90 degrees, the cosine rule a^2 = b^2 + c^2 - 2bc cos A simplifies to: A) a^2 = b^2 - c^2 B) a^2 = b^2 + c^2 C) a^2 = 2bc D) a^2 = b^2 + c^2 - 2bc Answer: B
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