IGCSE Maths / Introducing trigonometry

Missing side when the unknown is in the denominator revision notes

Edexcel International GCSE Maths (4MA1), chapter 16: Introducing trigonometry, specification point 4.8b-f. Part of the full course.

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Use sine, cosine or tan to find a missing side in a right-angled triangle. If the unknown side is underneath in the ratio, rearrange by dividing by the trigonometric ratio.

More lessons in Introducing trigonometry

• The sine ratio
• The cosine ratio
• The tangent ratio
• Labelling sides and choosing the trig ratio
• Finding a missing side with trigonometry
• Finding a missing angle with inverse trig
• Combining Pythagoras and trigonometry
• Two-step right-angled triangle problems
• Right-angled trigonometry with bearings
• Angles of elevation and depression