Chapter 5: Problem 21
\(\int \frac{d y}{\sqrt{y}(1-\sqrt{y})}=\) (A) \(4 \sqrt{1-\sqrt{y}}+C\) (B) \(\frac{1}{2} \ln |1-\sqrt{y}|+C\) (C) \(2 \ln (1-\sqrt{y})+C\) (D) \(-2 \ln |1-\sqrt{y}|+C\)
Short Answer
Expert verified
The correct answer is (D) \(-2 \ln |1-\sqrt{y}| + C\).
Step by step solution
01
Substitute Variables
Let \( u = \sqrt{y} \), which implies \( du = \frac{1}{2\sqrt{y}} dy \). This substitution makes \( dy = 2u \, du \). Substitute these into the integral.
02
Rewrite the Integral
The original integral becomes \( \int \frac{2u \, du}{u(1-u)} \). Cancel the \( u \) in the numerator and denominator to get \( 2 \int \frac{du}{1-u} \).
03
Integrate
The integral \( \int \frac{du}{1-u} \) is a standard form which results in \( -\ln|1-u| + C \). Therefore, the current integral evaluates to \( -2 \ln|1-u| + C \).
04
Substitute Back
Substitute back \( u = \sqrt{y} \) into the result. The final integral becomes \( -2 \ln |1-\sqrt{y}| + C \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Substitution Method
In calculus integration, the substitution method serves as a powerful tool to simplify complex integrals. Often, integrals contain functions or expressions that can be transformed into simpler forms by changing variables. By using a new variable, we can focus on a less complicated problem, making the integration process more manageable.
- Choose a substitution that simplifies the integral. For instance, in the example problem, by letting \( u = \sqrt{y} \), the radical component is replaced with a neat linear form.
- Modify the differential accordingly. If \( u = \sqrt{y} \), then \( du = \frac{1}{2\sqrt{y}} dy \) allows us to express \( dy \) in terms of \( du \), specifically \( dy = 2u \, du \).
- Rewrite your integral with the new variables. Substitute all appearances of the original variable and its differential with the new terms to achieve a simplified expression.
Exploring Definite and Indefinite Integrals
Integrals in calculus come in two primary types: definite and indefinite. These integrals are fundamental in understanding both areas under curves and the accumulation of functions.
- Indefinite integrals (or antiderivatives) are represented without upper and lower limits. Solving these integrals includes adding a constant \( C \), accounting for all possible functions with the given derivative. For example, solving \( \int \frac{1}{1-u} \, du \), where \( u = \sqrt{y} \), results in \( -\ln |1-u| + C \).
- Definite integrals include specific limits, representing the net area under the curve. These do not include the constant \( C \) in their final solution as the limits define a specific value.
The Role of Natural Logarithms in Integration
Natural logarithms are a vital part of calculus, especially in integration involving rational functions or expressions with exponential components. In the context of integration, they often emerge as results of specific integrals.
- The natural log, denoted by \( \ln \), arises frequently when integrating fractions where the denominator has a variable of degree one. For instance, in the integral \( \int \frac{du}{1-u} \), the solution leverages the natural logarithm: \( -\ln|1-u| \).
- Natural logs help solve more complex functions by transforming logarithmic differentiation into a straightforward form. This makes solving integrals like the one given simpler and more intuitive.
- Attention to absolute values is essential whenever \( \ln|x| \) appears, ensuring the function remains valid across all applicable input values.