Answer:
Explanation:
If the observer O spots a plane flying at a 55-degree angle to his horizontal, it means that the plane's flight path is inclined at an angle of 55 degrees with respect to the observer's line of sight on the ground. In other words, the plane is neither flying directly above O nor parallel to the ground. Instead, it is ascending or descending at an angle of 55 degrees relative to the observer's horizontal line of sight.
This angle is measured from the observer's line of sight on the ground, and it does not provide information about the plane's altitude or distance from the observer. To determine these factors, additional information, such as the plane's size, sound, or other reference points, would be necessary.