Answer:

8.39 meters

Step-by-step explanation:

The angle is opposite the side of interest of the right triangle representing the geometry. The adjacent side is known, so the tangent function can be useful.

Tan = Opposite/Adjacent

tan(40°) = width/(10 m) . . . . . filling in given values

(10 m)·tan(40°) = width ≈ 8.390996 m ≈ 8.39 m

The width of the river is about 8.39 meters.

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