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Answer:
5.3 m
Explanation:
The angle opposite the given side is ...
180° -105° -40° = 35°
Then the law of sines tells us the unknown distance (d) is ...
d/sin(40°) = 4.7 m/sin(35°)
d = (4.7 m)sin(40°)/sin(35°) ≈ 5.267 m
Denis will need to jump about 5.3 m to reach the neighboring roof.
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Additional comment
Denis will need a running start. The world record for a standing broad jump is less than 4 m.