Math Problem Statement

a bridge is being built across a canyon. the length of the bridge is 5065 ft. from the deepest point in the canyon, the angles of elevation of the ends of the bridge are 77 degrees and 72 degrees. how deep is the canyon?

Solution

To find the depth of the canyon, we can use trigonometric relationships involving the angles of elevation and the lengths involved. Let's denote:

  • AA as the point directly below the observer at the deepest point in the canyon.
  • BB and CC as the ends of the bridge, with AB=AC=xAB = AC = x (the horizontal distances from AA to BB and CC).
  • The angle of elevation to BB is 7777^\circ and to CC is 7272^\circ.

Using the tangent function, we have:

h=xtan(77)h = x \tan(77^\circ) h=(5065x)tan(72)h = (5065 - x) \tan(72^\circ)

Setting the two expressions for hh equal to each other gives us:

xtan(77)=(5065x)tan(72)x \tan(77^\circ) = (5065 - x) \tan(72^\circ)

Now we can solve for xx:

xtan(77)+xtan(72)=5065tan(72x \tan(77^\circ) + x \tan(72^\circ) = 5065 \tan(72^\circ x(tan(77)+tan(72))=5065tan(72)x(\tan(77^\circ) + \tan(72^\circ)) = 5065 \tan(72^\circ) x=5065tan(72)tan(77)+tan(72)x = \frac{5065 \tan(72^\circ)}{\tan(77^\circ) + \tan(72^\circ)}

Calculating the values for xx and then substituting back to find hh:

  1. Calculate tan(77)\tan(77^\circ) and tan(72)\tan(72^\circ).
  2. Solve for xx.
  3. Substitute xx into either equation to find hh.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Geometry

Formulas

h = x * tan(77°)
h = (5065 - x) * tan(72°)
x = (5065 * tan(72°)) / (tan(77°) + tan(72°))

Theorems

Tangent function in right triangles

Suitable Grade Level

Grades 10-12