The bearing of a harbour \(B\) from a boat \(A\) is \(072^\circ\). Write down the bearing of \(A\) from \(B\).
Question 1 Report
The bearing of a harbour \(B\) from a boat \(A\) is \(072^\circ\). Write down the bearing of \(A\) from \(B\).
Answer Details
A bearing is measured clockwise from north and is always written with three figures. The bearing of \(A\) from \(B\) is the back bearing of the bearing of \(B\) from \(A\), and the two differ by \(180^\circ\) because the north lines at \(A\) and at \(B\) are parallel, so the two bearings are co-interior angles that add to a straight turn.
The given bearing is less than \(180^\circ\), so add \(180^\circ\):
\[ 072 + 180 = 252 \]The bearing of \(A\) from \(B\) is \(252^\circ\). [B1]
The rule to remember is: if the given bearing is under \(180^\circ\), add \(180^\circ\); if it is \(180^\circ\) or more, subtract \(180^\circ\). Either way the answer must lie between \(000^\circ\) and \(360^\circ\).
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