Chapter 5: Problem 33
Completing the Square In Exercises \(33-42,\) find or evaluate the integral by completing the square. $$ \int_{0}^{2} \frac{d x}{x^{2}-2 x+2} $$
Short Answer
Expert verified
\(\frac{\pi}{2}\)
Step by step solution
01
Completing the Square
We have \(x^2 - 2x + 2\) as the denominator of our integral. We can write it as \((x - 1)^2 + 1\) using the formula \(a^2 - 2ab + b^2\) which is a perfect square, where \(a = x\) and \(b = 1\).
02
Substitution
Next, perform a substitution to get the integral into a standard form. Let \(u = x - 1\), then \(du = dx\). The integral becomes: \(\int \frac{du}{u^2 + 1}\).
03
Finding the Antiderivative
This integral now has the standard form \(\int \frac{du}{u^2 + 1}\), whose antiderivative is \(\tan^{-1}(u) + C\).
04
Substituting back and Finding the Definite Integral
First, the \(u\) should be replaced by \(x - 1\), to give us \(\tan^{-1}(x - 1) + C\). Secondly, place the original limits from \(0\) to \(2\), giving us: \[\tan^{-1}(2 - 1) - \tan^{-1}(0 - 1) = \tan^{-1}(1) - \tan^{-1}(-1)\] which simplifies to \(\frac{\pi}{4} - (-\frac{\pi}{4}) = \frac{\pi}{2}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
A definite integral is a key concept in calculus used to find the area under a curve over a specified range. Unlike indefinite integrals, which represent a family of functions, definite integrals yield a numerical value.
In our problem, we evaluate the integral from 0 to 2, meaning we look for the area under the curve defined by the function \ \( \frac{1}{x^2 - 2x + 2} \ \) between these two limits.
This process provides the net area, taking into account any portions of the curve that fall below the x-axis.
In our problem, we evaluate the integral from 0 to 2, meaning we look for the area under the curve defined by the function \ \( \frac{1}{x^2 - 2x + 2} \ \) between these two limits.
- The endpoints are denoted by the numbers 0 and 2 at the integral's bounds.
- You're not just finding an expression, but an exact numeric value from a specific interval.
This process provides the net area, taking into account any portions of the curve that fall below the x-axis.
Substitution Method
The substitution method is a powerful and commonly used technique to simplify complex integrals. It is essentially a change of variable that makes the integral easier to evaluate.
- Identify a part of the integrand complicating the process, often something squared or under a square root.
- Replace it with a simpler variable, say \(u\). For our integral, \(x - 1\) was replaced with \(u\).
- Determine the corresponding derivative. Here, \(du = dx\).
Antiderivative
Finding the antiderivative is like working backwards from a derivative. It's the process of calculating the function whose derivative is the function you're integrating.
For the integral \ \( \int \frac{du}{u^2 + 1} \ \), we know that its antiderivative is \( \tan^{-1}(u) + C \), where \(C\) is the constant of integration. This step is crucial because:
For the integral \ \( \int \frac{du}{u^2 + 1} \ \), we know that its antiderivative is \( \tan^{-1}(u) + C \), where \(C\) is the constant of integration. This step is crucial because:
- It converts our simplified integrand back into a function.
- If it's a definite integral like in our problem, you evaluate this antiderivative within the specified limits (between 0 and 2 in this case).
Trigonometric Integration
Trigonometric integration typically involves integrals where the integrand is a trigonometric function. In our case, the problem transitions into trigonometric integration once the substitution leads to the integral \ \( \int \frac{du}{u^2 + 1} \ \).
- The function \( \frac{1}{u^2 + 1} \) is commonly encountered and directly related to the arctangent function, \( \tan^{-1}(u) \).
- This highlights the importance of recognizing trigonometric identities and their derivatives which assist in solving these integrals.