(Sourcing) Who is David Stuart? Do you think he is a reliable source for learning about these monuments? Explain.

David Stuart is the David and Linda Schele Professor of Mesoamerican Art and Writing at the University of Texas at Austin.

David Stuart is a professor of archaeology at the University of Texas at Austin, who studies classic Maya society and a reliable source because he is a archaeology.

Explanation:

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Given that the diagram shows the location of John and Mark in relationship to the top of the building labeled A, then:
a]
∠4 is the angle of elevation as seen by Mark from his location. It is the angle between the horizontal and the line from the object to the observer's eyes.

b]
∠3 is the angle of depression and it is congruent to the angle 5, which is the angle of elevation as seen by John from his location.