The distance across the river, given the angle of the line of sight and the
distance along the shoreline is found using trigonometric ratios.
- The distance across the river is approximately 193 feet.
Reasons:
The distance along the the shore Shawna walked before sighting across the river = 90 feet
The angle made by the line of sight and the shoreline, θ = 65°
Required:
The distance across the river.
Solution:
Taking the initial location of Shawna to be the closest place to point she wanted to go across the river, we have;
The shortest distance across the river = A perpendicular line
Therefore, the following sides, form a right triangle;
- The line of sight.
- The distance along the shoreline Shawna walked, and
- The closest distance across the river.
Where:
The line of sight = The hypotenuse side
The distance she walked = The adjacent side to angle 65° angle
The closest distance across the river = The opposite side to the 65° angle
By trigonometric ratio, we have;
- [tex]\displaystyle tan(\theta) = \frac{Opposite \, side \, to\ angle}{Adjacent\, side \, to\, angle} = \mathbf{\frac{Distance \ across \ the \ river}{Distance \ along \ the \ shoreline}}[/tex]
Which gives;
Opposite side to angle = tan(θ) × Adjacent side to angle
Therefore;
Distance across the river = tan(65°) × 90 feet ≈ 193.0 feet
- The distance across the river is approximately 193 feet
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