Chapter 5: Problem 19
Use a definite integral to find the area under each curve between the given \(x\) -values. For Exercises \(19-24\) also make a sketch of the curve showing the region. $$ f(x)=x^{2} \text { from } x=0 \text { to } x=3 $$
Short Answer
Expert verified
The area under the curve is 9 square units.
Step by step solution
01
Understand the Problem
We need to find the area under the curve of the function \( f(x) = x^2 \) from \( x = 0 \) to \( x = 3 \). This area can be calculated using a definite integral.
02
Set Up the Integral
To find the area under the curve \( f(x) = x^2 \) from \( x=0 \) to \( x=3 \), we need to evaluate the definite integral: \[ \int_{0}^{3} x^2 \, dx \].
03
Integrate the Function
Next, we integrate the function \( x^2 \). The integral of \( x^n \) is \( \frac{x^{n+1}}{n+1} \). Therefore, \[ \int x^2 \, dx = \frac{x^3}{3} + C \], where \( C \) is the constant of integration.
04
Evaluate the Definite Integral
Now, evaluate the definite integral from \( x=0 \) to \( x=3 \):\[ \left[ \frac{x^3}{3} \right]_{0}^{3} = \frac{3^3}{3} - \frac{0^3}{3} = \frac{27}{3} - 0 = 9 \].
05
Interpret the Result
The result from evaluating the integral is 9. This means the area under the curve \( f(x) = x^2 \) from \( x = 0 \) to \( x = 3 \) is 9 square units.
06
Sketch the Graph
Sketch the graph of \( f(x) = x^2 \) from \( x = 0 \) to \( x = 3 \). The graph is a parabola opening upwards, and the area under the curve between these points is the region between the parabola and the x-axis over the interval [0, 3].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Area Under a Curve
The concept of finding the area under a curve is crucial in calculus. This technique determines the total space enclosed between the curve and the x-axis over a specific interval. It's especially useful for calculating physical quantities such as distance, where the curve represents speed.
- Definite Integrals: To find this area, we use definite integrals. A definite integral calculates the accumulation of quantities, such as areas, over a given interval. It is denoted by the integral sign with limits of integration, like this: \( \int_{a}^{b} f(x) \, dx \).
- Bounding Intervals: The limits of integration, 'a' and 'b', define the exact interval on the x-axis over which you're calculating the area. For this exercise, the bounds are from \(x = 0\) to \(x = 3\).
Integration Techniques
Integration techniques are methods used to calculate the integral of a function, playing a key role in finding areas under curves.
- Power Rule: One fundamental technique is the power rule, which simplifies finding integrals of polynomials. For a function \(x^n\), its integral is \(\frac{x^{n+1}}{n+1} + C\), where \(C\) is the integration constant. This was used in our exercise to integrate \(x^2\), yielding \(\frac{x^3}{3} + C\).
- Definite vs. Indefinite Integrals: While indefinite integrals contain a constant \(C\), definite integrals eliminate it by considering specific boundaries. This results in a particular numerical result rather than a family of curves. In our task, we moved from an indefinite to a definite integral by applying limits from \(x=0\) to \(x=3\).
Parabolic Functions
Parabolic functions, like \(f(x) = x^2\), are a standard type of quadratic polynomial known for their characteristic U-shaped curve. These functions are fundamental in algebra and calculus due to their simplicity and wide applicability.
- Basic Shape: The graph of \(f(x) = x^2\) is a parabola opening upwards. Every parabola has a vertex, which is the bottom point of the curve for upward opening parabolas. Here, the vertex is at \((0,0)\).
- Symmetry: Parabolas have a line of symmetry, which in this case is the y-axis. This means the curve is mirrored equally on either side of this axis.
- Application in Integration: When determining the area under a parabolic curve between two points, the integration gives the exact measure of the space below the arc of the parabola, down to the x-axis. In our example, the area between \(x=0\) and \(x=3\) was found to be 9 square units.