Math Problem Statement

Se va a fabricar un canal, de forma que su sección transversal sea un trapecio isósceles, en donde a = 4 metros y b = 6 metros (ver figura). Si el canal mide 200 metros. ¿Cuál es el volumen máximo?

Solution

To solve the problem of determining the maximum volume of the canal, we need to calculate the volume of the canal by considering its cross-sectional area and length. Here's the step-by-step process:

Step 1: Cross-sectional area of the isosceles trapezoid

The area AA of a trapezoid is given by: A=12(a+b)yA = \frac{1}{2} (a + b) y where:

  • a=4ma = 4 \, \text{m} (the shorter base),
  • b=6mb = 6 \, \text{m} (the longer base),
  • yy (the height of the trapezoid).

From the diagram, yy depends on the slope θ\theta of the sides, so: y=xtan(θ)y = x \tan(\theta) where xx is half the horizontal difference between bb and aa, given by: x=ba2=642=1m.x = \frac{b - a}{2} = \frac{6 - 4}{2} = 1 \, \text{m}.

Thus: y=tan(θ).y = \tan(\theta).

Step 2: Volume of the canal

The canal has a length of L=200mL = 200 \, \text{m}. Its volume VV is: V=AL=12(a+b)yL.V = A \cdot L = \frac{1}{2} (a + b) y \cdot L.

Substituting y=tan(θ)y = \tan(\theta): V=12(a+b)tan(θ)L.V = \frac{1}{2} (a + b) \tan(\theta) \cdot L.

Substituting the known values a=4a = 4, b=6b = 6, and L=200L = 200: V=12(4+6)tan(θ)200.V = \frac{1}{2} (4 + 6) \tan(\theta) \cdot 200. V=1000tan(θ).V = 1000 \tan(\theta).

Step 3: Maximize the volume

To maximize VV, we need to find the angle θ\theta that maximizes tan(θ)\tan(\theta), under the constraint that the trapezoid remains physically possible. The maximum feasible θ\theta depends on practical design limits (e.g., the slope of the sides).

Result:

The volume VV depends directly on tan(θ)\tan(\theta), and maximizing tan(θ)\tan(\theta) maximizes VV. If there's a specific angle constraint or other details you'd like analyzed, please clarify, and I can refine the solution!

Would you like further clarifications or an extended explanation?


Here are 5 related questions for deeper understanding:

  1. What practical constraints might limit the angle θ\theta in the construction of the canal?
  2. How does the volume change if the length LL of the canal is reduced?
  3. What happens to the volume if the width bb of the top base is increased?
  4. How does the design of the canal affect water flow efficiency?
  5. Can you analyze the structural stability of the canal for different slopes θ\theta?

Tip: Always check feasibility constraints (like slope and material strength) when maximizing geometric quantities!

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Math Problem Analysis

Mathematical Concepts

Geometry
Calculus
Optimization

Formulas

Area of a trapezoid: A = (1/2) * (a + b) * y
Volume of a prism: V = A * L
Relationship for height y: y = x * tan(θ)

Theorems

Maximization of a function using calculus

Suitable Grade Level

Grades 10-12