California Assessment of Student Performance and Progress (CAASPP) Math Practice Exam

Measuring an angle of depression involves looking downward from a particular point to an object that is below that point. In this context, observing a bird flying at a lower altitude fits this definition, as you are situated above the bird's flight path and need to look down to see it. The angle formed between the horizontal line of sight from your position and the line of sight to the bird is the angle of depression.

The other scenarios do not represent measuring an angle of depression. For instance, looking up at a mountain peak involves an angle of elevation, as you are viewing something higher than your current position. Reading a book on a table occurs at the same level, so there is no upward or downward angle to measure. Finally, gazing at the top of a skyscraper from the street also represents an angle of elevation, as you're looking up from ground level to a point that is higher than where you are standing. Thus, observing a bird flying at a lower altitude is the only scenario that accurately describes measuring an angle of depression.