Question

In Exercises \(45-48\), use a graphing utility to graph the region bounded by the graphs of the equations. Use the integration capabilities of the graphing utility to approximate the centroid of the region. $$ y=10 x \sqrt{125-x^{3}}, y=0 $$

Short answer

The process involves plotting the equations, finding the bounded area, and using integration to calculate the centroid. The exact centroid coordinates would typically need a numerical approximation method or software to compute.

Step-by-step solution

Plotting the Equations

The first step is to plot the given equations \(y = 10x \sqrt{125 - x^3}\) and \(y = 0\) on a graphing utility. The resulting graph will visually represent the area under the curve.

Finding the Bounded Region

The bounded region is the area between \(y = 10x \sqrt{125 - x^3}\) and the x-axis, from the left endpoint of the curve to the right endpoint.

Using Integration to Find the Centroid

To find the x-coordinate of the centroid, an integral of the form \(\frac{1}{A} \int_a^b x f(x) dx\) is used. In this case, \(f(x) = 10x \sqrt{125 - x^3}\). To find the y-coordinate of the centroid, an integral of the form \(\frac{1}{A} \int_a^b \frac{f(x)^2}{2} dx\) is used. In this integral, \(A\) is the area of the region, \(a\) and \(b\) are the left and right endpoints of the region, and \(f(x)\) is the function in question. These integrals can usually be calculated with the help of a graphing utility.

Key concepts

Graphing Utility

A graphing utility is a tool often used in mathematics, particularly for visualizing functions and their properties. It can be software or an online application that allows users to input functions and instantly see the graphed results on a coordinate plane. This visual representation is invaluable for understanding complex relationships between variables.

For instance, in the problem at hand, the graphing utility shows the shape of the graph of the equation \( y = 10x\sqrt{125 - x^3} \). Seeing the curve helps to identify the bounded region which is crucial before we can proceed with the calculus involved in finding the centroid of the area. Graphing utilities also often come with built-in integration capabilities. Therefore, after identifying the region, the same utility can be used to approximate the centroid, seamlessly transitioning from a visual step to a computational one.

Integral Calculus

Integral calculus is one of the two principal branches of calculus, with the other being differential calculus. Integral calculus focuses on the accumulation of quantities, such as areas under curves. By integrating a function, we can find the total value that the function accumulates over a certain interval.

When you come across a problem like finding the centroid of a region bounded by curves, integral calculus is the technique you would employ. The process involves setting up integrals that correspond to the balanced measurements of the region's distribution of mass. Generally, the formula for the centroid involves the calculation of two integrals: one for the x-coordinate and one for the y-coordinate. Each integral takes into account the specific geometry of the function, as well as the area of the region in question. Integral calculus transforms the problem from a geometric one into a numerical question, providing a precise location for the centroid, which is the 'center of mass' for a two-dimensional region.

Area Under a Curve

The area under a curve is a foundational concept in integral calculus. It represents the accumulation of infinitesimally small rectangles under the path a curve takes from one point to another. The total area can be found using definite integrals, which calculate the sum of these miniature areas from the starting point, or lower limit, to the ending point, or upper limit of integration.

When working with the problem given, the function \( y = 10x \sqrt{125 - x^3} \) plotted against \( y = 0 \), which is simply the x-axis, outlines the area of interest. The graphing utility can numerically integrate this function to find the area of the region bounded by the curve and the x-axis. Understanding how this area is calculated is critical when solving for the centroid, as it's necessary to weigh the integrals for the centroid coordinates against this area. Graphing utilities simplify this usually complex process, making it more accessible to students and allowing them to focus on understanding the concepts rather than getting bogged down in computation.