IGCSEMaths: ExtendedCIERevision NotesPythagoras & TrigonometrySine, Cosine Rule & Area of TrianglesArea of a Triangle

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First teaching 2023

First exams 2025

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Area of a Triangle (CIE IGCSE Maths: Extended)

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CIE Maths: ExtendedEdexcel Maths A (Modular): Higher Unit 1Cambridge (CIE) International 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!
  • The formula for the area of a triangle can be found in the list of formulas on page 2

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

    Expertise: Maths

    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.