4.8.7

Area of a Triangle

Test yourself

Area of a Triangle

We can use the formula: area of a triangle = 12ab sin(C).

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Formula

  • Area of a triangle = 12ab sin(C) since the vertical height is b sin(C).
  • This formula can also be used to calculate the side length of a triangle whose area is known.
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Example

  • If we are given a triangle with two sides of 8cm and 10cm and the area is 20cm2, we can calculate the angle between the sides as follows:
    • 20 = 12 × 8 × 10 × sin(C)
    • 20 = 40 × sin(C)
    • sin(C) = 12
    • C = 30°

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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