A boat is heading towards a lighthouse, whose beacon-light is 113 feet above the water. The boat’s crew measures the angle of elevation to the beacon, 11∘. What is the ship’s horizontal distance from the lighthouse (and the shore)?
Q. A boat is heading towards a lighthouse, whose beacon-light is 113 feet above the water. The boat’s crew measures the angle of elevation to the beacon, 11∘. What is the ship’s horizontal distance from the lighthouse (and the shore)?
Understand and Visualize: Understand the problem and visualize the scenario.We have a right triangle where the lighthouse is the vertical side (opposite to the angle of elevation), the horizontal distance from the boat to the lighthouse is the adjacent side, and the angle of elevation is given as 11 degrees.
Identify Trigonometric Function: Identify the trigonometric function to use.To find the horizontal distance (adjacent side), we use the cosine function, which relates the adjacent side to the hypotenuse in a right triangle.cos(θ)=hypotenuseadjacent
Set up Equation: Set up the equation using the cosine function. cos(11∘)=113 feethorizontal distance
Solve for Distance: Solve for the horizontal distance.horizontal distance = 113 feet×cos(11°)Now we calculate the cosine of 11 degrees and multiply it by 113 feet.
Calculate Cosine and Multiply: Calculate the cosine of 11 degrees and multiply by 113 feet.Using a calculator, we find that cos(11∘)≈0.9816.Therefore, horizontal distance ≈113 feet ×0.9816
Perform Multiplication: Perform the multiplication to find the horizontal distance. horizontal distance ≈113 feet×0.9816≈110.9408 feet
Round Answer: Round the answer to a reasonable degree of precision.Since the angle was given to two significant figures, we can round the horizontal distance to the nearest foot.horizontal distance ≈111 feet
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