First, let us consider the definitions used in this problem:
- Magnetic variation - the angle between true (geographical) north and the magnetic north.
- True (magnetic) bearing - the angle measured clockwise from true north to the object.
- Annual magnetic declination - the change in degrees per a year.
Therefore, determine the magnetic bearing of the Island after 36 years with annual decrease (negative annual declination) of 15':
M36=80∘10′+36⋅(−0∘15′)=71∘10′.Determine the magnetic variation of the Island by 31st October 2018, after 32 years:
M32=80∘10′+(2018−1986)⋅(−0∘15′)==72∘10′.
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