Bearings

Bearings

Secondary 3
  1. In Mathematics, the study of bearings enables us to tell the position of objects with reference to one another.
  2. Two important things about bearing:
    • Angle (in degree), measured clockwise from the north direction.
    • Must always be stated in three digits. with \(000^\circ\leq\theta<360^\circ\)
  3. Let’s look at the diagram below.

Find the bearing of \(B\) from \(A\).

  • Join \(A\) and \(B\).

  • Construct \(N\) at reference point \(A\).

  • Measure angle clockwise from \(N\) of reference point \(A\).

The bearing of \(B\) from \(A\) is \(035{}^\circ\).

Find the bearing of \(A\) from \(B\).

  • Join \(A\) and \(B\).

  • Construct \(N\) at reference point \(B\).

  • Measure angle clockwise from \(N\) of reference point \(B\).

The bearing of \(A\) from \(B\) is \(215{}^\circ\).

Bearing of \(A\) from \(B\) is not the same as the bearing of \(B\) from \(A\).

  1. The following are \(3\) angle properties involving straight line:
    • Alternate angle
    • Corresponding angle
    • Interior angle
    are used quite often to find the bearings.
  2. Know the directions
    List item image
  3. Problem involving Bearings
    May involve the use of Sine Rule
    • Sine Rule
    \(\frac{a}{\sin A} = \frac{b}{\sin B} = \frac{c}{\sin C}\) used when there are two given sides and one non-included angle, or when they are two given angles and one given side.
    • Cosine Rule
    \(c^2 = a^2 + b^2 - 2ab \cos C\) used when there are two given sides and one included angle, or when all three sides are given.

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Answer:Bearings are measured clockwise from north and written using three digits. In the example, the bearing of \(B\) from \(A\) is \(035^\circ\), while the bearing of \(A\) from \(B\) is \(215^\circ\).

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