Final answer:
Point 'A' with an angle of dip of +25° is in the northern hemisphere, while point 'B' with an angle of dip of −25° is in the southern hemisphere. The angle of dip provides information about whether magnetic field lines are dipping towards or away from the Earth, indicating the location's hemisphere.
Step-by-step explanation:
If at point 'A' on the Earth's surface, the angle of dip is δ = +25°, and at a point 'B', it is δ = −25°, we can interpret that these points are located in different hemispheres. The angle of dip, also known as magnetic inclination, is the angle made with the horizontal by the Earth's magnetic field lines. Positive values of the angle of dip suggest that the location is in the northern hemisphere, where the magnetic field lines are dipping towards the Earth. Conversely, negative values imply that the location is in the southern hemisphere, where the magnetic field lines are dipping away from the Earth. Therefore, point 'A' is in the northern hemisphere and point 'B' is in the southern hemisphere.
Just by knowing the angle of dip, we can determine the hemisphere of a location. To be clear, if the angle of dip were positive at both A and B, only then could we infer that both points are in the southern hemisphere; as it is, point A with a positive dip angle is in the northern hemisphere.