Math Problem Statement

A bridge is being built across a canyon. The length of the bridge is 5025 ft. From the deepest point in the canyon, the angles of elevation of the ends of the bridge are 75° and 73°. How deep is the canyon?

Solution

To solve this problem, we can use trigonometry, specifically the tangent function, which relates the height (hh) to the given angles and distance across the canyon.

Given Information:

  • The distance across the canyon (the length of the bridge) is 50255025 feet.
  • The angles of elevation to the ends of the bridge from the deepest point in the canyon are 7575^\circ and 7373^\circ.

Steps:

Let's label the midpoint directly below the bridge as OO and the points where the angles are taken from as AA and BB at the ends of the bridge.

  1. Divide the bridge into two right triangles where:

    • One triangle has an angle of 7575^\circ and half the bridge distance, 50252=2512.5\frac{5025}{2} = 2512.5 feet.
    • The other triangle has an angle of 7373^\circ and the same horizontal distance of 2512.52512.5 feet.
  2. Apply the tangent function:

    • For the triangle with the 7575^\circ angle: tan(75)=h2512.5\tan(75^\circ) = \frac{h}{2512.5} Solving for hh: h=2512.5×tan(75)h = 2512.5 \times \tan(75^\circ)

    • For the triangle with the 7373^\circ angle: tan(73)=h2512.5\tan(73^\circ) = \frac{h}{2512.5} Solving for hh: h=2512.5×tan(73)h = 2512.5 \times \tan(73^\circ)

  3. Calculate the depths: Plugging in the values for tan(75)\tan(75^\circ) and tan(73)\tan(73^\circ) using a calculator:

    • tan(75)3.732\tan(75^\circ) \approx 3.732
    • tan(73)3.271\tan(73^\circ) \approx 3.271

    Then:

    • For 7575^\circ: h2512.5×3.732=9375.63h \approx 2512.5 \times 3.732 = 9375.63 feet
    • For 7373^\circ: h2512.5×3.271=8222.24h \approx 2512.5 \times 3.271 = 8222.24 feet

Final Answer

The canyon is approximately 82228222 feet deep (rounded to the nearest foot).


Would you like further details or clarification on any step?

Relative Questions

  1. How would the solution change if the angles of elevation were different?
  2. What trigonometric identities are used to derive the tangent function?
  3. How can you verify if the depth calculation is correct?
  4. Can this method be used if the bridge were not straight across?
  5. How would the answer change if the length of the bridge increased?

Tip

In trigonometric problems involving elevation angles, it’s helpful to split complex shapes into right triangles to use tangent or other trigonometric ratios effectively.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Right Triangles
Tangent Function

Formulas

tan(θ) = opposite / adjacent

Theorems

Right Triangle Trigonometry

Suitable Grade Level

Grades 10-12