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Using bearings in trigonometryBearings

Bearings are angles used in navigation. They are based on moving clockwise from due north. Missing information about bearings can be worked out using the sine and cosine rules.

Part of MathsTrigonometric skills

Bearings

In mathematics, a bearing is the angle in degrees measured clockwise from north.

Bearings are usually given as a three-figure bearing. For example, 30掳 clockwise from north is usually written as 030掳.

Problems involving bearings can be worked out as you would work out problems with triangles using the sine or cosine rule:

  • Use the cosine rule when:
    • you need to find a side and you know two sides and the included angle
    • you need to find an angle (or bearing) and you know three sides
  • Use the sine rule when:
    • you need to find a side and you know one sides and three angles
    • you need to find an angle (or bearing) and you know two sides and an angle