Final answer:
To go from magnetic to true heading, subtract the variation angle from the magnetic heading. To go from true to magnetic heading, add the variation angle to the true heading.
Step-by-step explanation:
When going from magnetic to true, you need to subtract the variation angle (VAR) from the magnetic heading. VAR is the angle between true north and magnetic north at a specific location. Subtracting this angle will give you the true heading.
When going from true to magnetic, you need to add the variation angle (VAR) to the true heading. Again, VAR is the angle between true north and magnetic north at a specific location. Adding this angle will give you the magnetic heading.
For example, if you have a magnetic heading of 120 degrees and the variation angle (VAR) is -5 degrees (meaning magnetic north is 5 degrees west of true north), to find the true heading you would subtract -5 degrees from 120 degrees, resulting in a true heading of 125 degrees.