IGCSE Maths / Further trigonometry

Area of a triangle using half ab sin C

Edexcel International GCSE Maths (4MA1), chapter 25: Further trigonometry, specification point 4.8e. Part of the full course.

Read the revision notes · IGCSE Maths past papers

The formula ½ab sin C finds the area of any triangle when you know two sides and the angle between them. It avoids needing a right angle or a marked height.

More lessons in Further trigonometry

• The sine rule: finding a missing side
• The sine rule: finding a missing angle
• The ambiguous case of the sine rule
• The cosine rule: finding a missing side
• The cosine rule: finding a missing angle
• Choosing between the sine rule and the cosine rule
• Finding a side or an angle from a given area
• Area of a segment
• The angle between a line and a plane
• Trigonometry in pyramids and cones
• Problem solving in three dimensions