Chapter 5: Problem 30
\(\int \frac{\cos x d x}{\sqrt{1+\sin x}}=\) (A) \(-\frac{1}{2}(1+\sin x)^{1 / 2}+C\) (B) \(\ln \sqrt{1+\sin x}+C\) (C) \(2 \sqrt{1+\sin x}+C\) (D) \(\ln |1+\sin x|+C\)
Short Answer
Expert verified
The answer is (C) \(2 \sqrt{1+\sin x}+C\).
Step by step solution
01
Identify the Substitution
We start by recognizing the form of the integrand. Notice that the derivative of \(1 + \sin x\) is \(\cos x\). This suggests using the substitution \(u = 1 + \sin x\). Then, \(du = \cos x \ dx\).
02
Substitute and Simplify
Substitute the identified \(u\) into the integral. The integral becomes \(\int \frac{1}{\sqrt{u}} \, du\).
03
Integrate with Respect to u
The integral \(\int \frac{1}{\sqrt{u}} \, du\) can be calculated as \(2\sqrt{u} + C\). This is a standard integral result for \(u^{-1/2}\).
04
Back-Substitute
Replace \(u\) back to the original variable \(x\). Since \(u = 1 + \sin x\), substitute back to get \(2\sqrt{1 + \sin x} + C\).
05
Match with Given Options
Compare the solved integral \(2\sqrt{1 + \sin x} + C\) with the options given. We find that it matches option (C).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integration Techniques
Integration is a fundamental concept in calculus, serving as the reverse process of differentiation. It enables us to accumulate quantities, track areas under curves, and solve a wide variety of mathematical problems. There are several techniques available for solving integrals:
- **Basic Integration**: Use basic integration formulas for simple expressions such as polynomials.
- **Substitution Method**: Simplifies the integration process by transforming the expression into a more easily integrable form.
- **Integration by Parts**: Useful when dealing with products of functions by reducing the integral to a simpler form.
- **Partial Fraction Decomposition**: Breaks complex rational functions into simpler fractions to simplify integration.
U-Substitution
The substitution method, often called "u-substitution," is a powerful technique used in integral calculus to simplify integrations. This approach involves changing variables to make an integral more manageable to solve. The general idea starts with picking a substitution, which can turn a complicated integral into a simpler one.
Here are the steps for u-substitution:
Here are the steps for u-substitution:
- Identify a part of the integral that could simplify the process when substituted with a new variable, denoted as "u".
- Calculate the differential of "u", giving you "du" in terms of the original variable and differential.
- Replace the original variable and differential in the integral with "u" and "du", transforming the integral.
- Solve the transformed integral—often using known rules and simpler expressions.
- Back-substitute the original variables back to express the answer in terms of the initial variable.
Trigonometric Integrals
Trigonometric integrals are integrals that involve trigonometric functions like \( \sin x \) and \( \cos x \). These functions often appear in calculus problems, especially in physics and engineering contexts due to their periodic nature.
There are several strategies to tackle trigonometric integrals:
There are several strategies to tackle trigonometric integrals:
- **Standard Trigonometric Identities and Formulas**: Sometimes, using identities such as \( \sin^2 x + \cos^2 x = 1 \) or \( \sin(2x) = 2\sin x\cos x \) can simplify the integral.
- **Substitution**: As demonstrated in the problem, substitution can simplify expressions that involve trigonometric functions by transforming them into more familiar algebraic forms.
- **Power Reduction and Trigonometric Substitutions**: Techniques involving reducing powers of trigonometric functions or substituting with identities can help solve more complex integrals.
Definite Integral Evaluation
Definite integrals represent the accumulation of a quantity over a specific interval. Unlike indefinite integrals that yield a general function plus a constant, definite integrals provide a specific numerical value essential for applications like finding areas under curves.
Here is the typical process of evaluating definite integrals:
Here is the typical process of evaluating definite integrals:
- Set up the integral by identifying the limits of integration, which describe the interval over which you are integrating.
- Use an appropriate integration technique to evaluate the integral in terms of an antiderivative.
- Apply the **Fundamental Theorem of Calculus**, which connects the evaluation of definite integrals to antiderivatives. It involves calculating the difference between the values of the antiderivative at the upper and lower limits.
- Calculate to get the numerical result, which is the exact area under the curve within the bounds specified.