The back bearing (reverse bearing) may be calculated by adding or subtracting 180° from the original bearing. The result must fall between 0° and 360°.
- If the original bearing is less than 180°, add 180° to it.
- If original bearing is greater than 180°, subtract 180° from it.
a: 124 + 180 = 304º
b: 68 + 180 = 248º
c: 244 - 180 = 64º
d: 321 - 180 = 141º
