Right-angled Triangles
Overview
Trigonometry connects the angles of a right-angled triangle to the lengths of its sides, and that link is one of the most powerful tools in mathematics. With it you can find a height you cannot climb, a distance you cannot pace out, or an angle you cannot reach a protractor to.
In this lesson you will use the sine, cosine and tangent ratios to find sides and angles in right-angled triangles, and solve two-dimensional problems with these ratios and Pythagoras' theorem. (At Extended you will also handle angles of elevation and depression.)
Objectives
- Know and use the sine, cosine and tangent ratios for acute angles in calculations involving sides and angles of a right-angled triangle.
- Solve problems in two dimensions using Pythagoras’ theorem and trigonometry.
- Know that the perpendicular distance from a point to a line is the shortest distance to the line. (Extended only)
- Carry out calculations involving angles of elevation and depression. (Extended only)
Audio Lesson
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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 Right-angled Triangles. 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 ratio is sin θ? A. opp/adj B. adj/hyp C. opp/hyp D. hyp/opp Answer: C
- A right-angled triangle has hypotenuse 10 cm and an angle of 30°. The opposite side is: A. 5 cm B. 8.66 cm C. 10 cm D. 20 cm Answer: A
- If tan θ = 3/4, then θ is: A. 30.0° B. 36.9° C. 45.0° D. 53.1° Answer: B
- Which side is the hypotenuse? A. opposite the angle θ B. opposite the right angle C. next to θ D. the shortest side Answer: B
- To find an unknown angle from two known sides you use: A. the ratio directly B. Pythagoras C. the inverse trig function D. the area formula Answer: C
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