Problem

If a person’s moon shadow is reflected in the water, its length is $10 ft$ from the feet, and the height from the water’s surface to the eyes is $6 ft$, How many degrees does the moon hang over?

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Solution

Let the elevation angle of the moon be $θ$.

Then, since $AB=10$ is the length of the moon shadow, and $BC=6$ is the eye height in the figure, 

$$tan⁡θ=\frac{6}{10}=0.6,$$

$$∴ \ θ≒30°57’49.52^”.$$

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$$(Answer) \quad Approximately  \ 30°57’49.52^”.$$

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Reference

Yoshikazu Yamakawa, ed. (1997) Okayama ken no Sangaku (Sangaku in Okayama Prefecture), p.48; p.315.