IGCSEMaths: ExtendedCIERevision Notes3. Geometry3.10 Sine, Cosine Rule & Area of Triangles3.10.2 Area of a Triangle

Syllabus Edition

First teaching 2021

Last exams 2024

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Area of a Triangle (CIE IGCSE Maths: Extended)

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Area of a Triangle

How do I find the area of a non-right triangle?

  • The area of any triangle can be found using the formula

A space equals space 1 half a b sin C

    • Where C is the angle between sides a and b
  • Be careful to label your triangle correctly so that C is always the angle between the two sides
  • Sin 90° = 1 so if C = 90° this becomes Area = ½ × base × height

 

Examiner Tip

  • Remember to check that your calculator is in degrees mode!

Worked example

The following diagram shows triangle ABC. AB space equals space 32 space cm, AC space equals space 1.1 space straight m, B A with hat on top straight C space equals space 74 degree.  3-3-2-area-rule-we-question

Calculate the area of triangle .

3-3-2-ai-sl-area-rule-we-solution

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    Amber

    Author: Amber

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    Amber gained a first class degree in Mathematics & Meteorology from the University of Reading before training to become a teacher. She is passionate about teaching, having spent 8 years teaching GCSE and A Level Mathematics both in the UK and internationally. Amber loves creating bright and informative resources to help students reach their potential.