Chapter 4: Problem 4
Find the area under the given curve over the indicated interval. $$ y=x^{2} ; \quad[0,3] $$
Short Answer
Expert verified
The area under the curve \( y = x^2 \) from 0 to 3 is 9.
Step by step solution
01
Understand the problem
We need to find the area under the curve of the function \( y = x^2 \) over the interval \([0, 3]\). This is essentially finding the definite integral of the function from 0 to 3.
02
Write the integral expression
The definite integral to find the area under the curve from \( x=0 \) to \( x=3 \) is written as: \[\int_{0}^{3} x^2 \, dx\]
03
Apply the power rule for integration
The power rule for integration states that \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \), where \( C \) is the constant of integration. For \( x^2 \), \( n = 2 \). Thus, the integral is \[\int x^2 \, dx = \frac{x^{3}}{3} + C\]
04
Evaluate the definite integral
Apply the limits of integration (from 0 to 3) to the antiderivative: \[\left. \frac{x^{3}}{3} \right|_{0}^{3} = \frac{3^{3}}{3} - \frac{0^{3}}{3} \]
05
Simplify the evaluation
Simplify the expression: \[\frac{3^{3}}{3} = \frac{27}{3} = 9\]So, the area under the curve from 0 to 3 is 9.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Area under Curve
Finding the area under a curve involves calculating the definite integral of a function over a specified interval. In this exercise, we are considering the function \( y = x^2 \) over the interval \([0, 3]\). This means we want to find the total area enclosed between the curve, the x-axis, and the vertical lines \(x = 0\) and \(x = 3\). The definite integral gives us this area by summing up an infinite number of infinitesimal rectangles under the curve. The definite integral
- summarizes areas added together within the limits of integration,
- can represent exact areas under the curve when calculated correctly.
Power Rule for Integration
The power rule for integration is a fundamental tool for finding antiderivatives, which allows us to solve integrals for polynomial functions like our given \( y = x^2 \). According to the power rule:
- For any function \( x^n \), the integral is \( \int x^n \, dx = \frac{x^{n+1}}{n+1} + C \)
- "\(C\)" represents the constant of integration,
- This rule only applies when \( n eq -1 \).
Antiderivative
The antiderivative, sometimes called the "indefinite integral," of a function is a function whose derivative is the original function. In simpler terms, finding the antiderivative is like reversing the process of differentiation. For a function \( x^2 \), its antiderivative based on the power rule is \( \frac{x^{3}}{3} + C \). To solve a definite integral, we need this antiderivative to evaluate the integral over a particular interval. Here, the function \( f(x) = \frac{x^3}{3} \) acts as the antiderivative of \( y = x^2 \), and crucially helps us compute the exact area under the curve between \( x = 0 \) and \( x = 3 \).
Evaluation of Integral
The evaluation of a definite integral involves applying the antiderivative to the upper and lower limits of the interval. In our problem for the integral \( \int_{0}^{3} x^2 \, dx \), the steps are:
- First, substitute \( x = 3 \) into the antiderivative \( \frac{x^3}{3} \), giving \( \frac{27}{3} = 9 \).
- Then substitute \( x = 0 \), which results in \( \frac{0^3}{3} = 0 \).
- upper value \(9 - 0\) from the lower value,
- leading to an area of 9 between \( x = 0 \) to \( x = 3 \).