What about regions built along a natural boundary? For example the maximum for both a rectangular region and a triangular region built along a natural boundary with 100 yards of fencing is 1250 sq. yds. But the rectangle is not the maximum area four-sided figure that can be built. What is the maximum-area four-sided figure?

For a four-sided figure, we should consider a trapezoid. Here's how we can do it:

Let's say the trapezoid is built alongside the natural boundary with its two bases parallel to the boundary. Let the lengths of the bases be b1 and b2, and let the height be h. To maximize the area of the trapezoid, the sum of the two non-parallel sides should be equal to the remaining fencing, which is 100 yards in this case.

Let x be the difference between the two bases, so that b2 = b1 + x. The area A of the trapezoid can be expressed as:

A = 0.5 * (b1 + b2) * h.

We can use the Pythagorean theorem to relate h and x to the length of the non-parallel sides of the trapezoid:

h^2 + (x/2)^2 = (50 - b1)^2.

Now, we substitute b2 = b1 + x in the area formula:

A = 0.5 * (b1 + b1 + x) * h = (b1 + 0.5x) * h.

We can solve for h from the Pythagorean theorem equation and substitute it into the area formula:

h = sqrt((50 - b1)^2 - (x/2)^2).

So, A = (b1 + 0.5x) * sqrt((50 - b1)^2 - (x/2)^2).

Now, to maximize the area A, we can take the derivative of A with respect to b1 and set the result equal to 0, and then solve for b1. We would also need to determine an expression for x in terms of b1. This would involve solving a system of equations and using calculus for optimization.

However, this approach is quite complex and, given the nature of the problem, is likely to require numerical methods for a solution. The maximum area for the trapezoid (a four-sided figure) built along the natural boundary can then be determined using those values of b1 and x. This value is expected to be greater than 1250 sq. yds, which is the maximum area for the rectangular and triangular regions mentioned.

To find the maximum area four-sided figure that can be built along a natural boundary with 100 yards of fencing, we can use the concept of calculus and optimization.

Let's consider a general quadrilateral with two sides parallel to the natural boundary and the other two sides perpendicular to it. Let's assume one of the perpendicular sides has a length of "x" yards, while the parallel side has a length of "y" yards. The other two sides (non-parallel to the natural boundary) will also have lengths of "x" and "y" yards.

To find the area of this quadrilateral, we need to find a function that expresses the area (A) in terms of "x" and "y". Since the area of a quadrilateral can be calculated as the product of its base and height, its area is given by:

A = x * y

Now, we need to consider the constraint that the total fencing material used should be 100 yards. Using the perimeter formula, we can write this constraint equation as:

2x + 2y = 100

Simplifying the equation, we have:

x + y = 50

Now, we want to find the maximum value of A subject to this constraint. We can solve this problem by using the method of Lagrange multipliers.

Define a new function F(x, y, λ) as:

F(x, y, λ) = A - λ(x + y - 50)

Where λ is the Lagrangian multiplier. We want to find the values of x and y that maximize F(x, y, λ).

To find the maximum, we need to find the critical points of F(x, y, λ). We take the partial derivatives of F with respect to x, y, and λ, and set them equal to zero:

∂F/∂x = 0 => y - λ = 0 (1)
∂F/∂y = 0 => x - λ = 0 (2)
∂F/∂λ = 0 => x + y - 50 = 0 (3)

From equations (1) and (2), we can see that x = y = λ.

Substituting this into equation (3), we have:

2x - 50 = 0
x = 25

Since x = y, the maximum area four-sided figure that can be built is a square with sides measuring 25 yards each. The area of this square is:

A = x * y = 25 * 25 = 625 square yards.

Therefore, the maximum-area four-sided figure that can be built along a natural boundary with 100 yards of fencing is a square with an area of 625 square yards.

To find the maximum-area four-sided figure that can be built along a natural boundary with 100 yards of fencing, we need to consider different shapes and calculate their respective areas. Let's go through the steps to find the answer!

1. Define the problem: We want to find a four-sided figure with the maximum area that can be formed using 100 yards of fencing, where one side is constructed along a natural boundary.

2. Analyze different shapes: We are given that a rectangular region and a triangular region both have a maximum area of 1250 sq. yds. But we need to find another shape with an even larger area.

3. Consider possible shapes: Since we are looking for a four-sided figure, the shape needs to have four sides. Let's consider various quadrilateral shapes, such as squares, parallelograms, trapezoids, and rectangles with irregular corners.

4. Calculate the areas: For each quadrilateral shape, calculate its area using the given information that we have 100 yards of fencing.

5. Compare the areas: Compare the areas of the different quadrilateral shapes we have calculated. Identify which shape has the largest area since that will be the maximum-area four-sided figure.

Once you have performed these steps, you should be able to determine the maximum-area four-sided figure that can be built along a natural boundary with 100 yards of fencing.