IP EMaths Notes (Upper Sec, Year 3-4): 09) Right-Triangle Trigonometry
In one line
Use sine, cosine, and tangent ratios alongside Pythagoras to evaluate sides and angles quickly.
Last updated 30 Nov 2025
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Read the summary above.
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Scan the first few sections below.
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Jump into the section that matches your decision.
- Start Here
- Ratio recap
- Worked example - Ladder against a wall
- Worked example - Find an acute angle from side lengths
Q: What does IP EMaths Notes (Upper Sec, Year 3-4): 09) Right-Triangle Trigonometry cover?
A: Use sine, cosine, and tangent ratios alongside Pythagoras to evaluate sides and angles quickly.
Start Here
| Read time | What to take away |
| 1 second | Pick sine, cosine, or tangent by matching the known sides to the marked angle. |
| 10 seconds | Label opposite, adjacent, and hypotenuse before choosing a ratio. Use inverse trig when the angle is unknown, and Pythagoras when two sides are known. |
| 100 seconds | Work through the ladder and flagpole examples to practise modelling a real picture as a right triangle, choosing the ratio, calculating, and checking that the units make sense. |
Right-angled triangles provide fast access to heights, bearings, and resultant forces. Remember which side is opposite, adjacent, or hypotenuse relative to the marked angle.
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These notes align with SEAB GCE O-Level Mathematics (4052) content used in IP programmes (exams from 2026).
Status: SEAB O-Level Mathematics 4052 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for these notes.
