Chapter 5: Problem 52
Evaluate the integrals using appropriate substitutions. $$ \int \frac{e^{\sqrt{2 y+1}}}{\sqrt{2 y+1}} d y $$
Short Answer
Expert verified
The integral evaluates to \( e^{\sqrt{2y+1}} + C \).
Step by step solution
01
Identify the Inner Function for Substitution
Recognize that the expression under the square root, \( \sqrt{2y+1} \), complicates the integration. Define a substitution to simplify the integral. Let \( u = \sqrt{2y+1} \), which implies that \( u^2 = 2y + 1 \).
02
Differentiate and Solve for dy
Take the derivative of both sides with respect to \( y \) to find \( dy \) in terms of \( du \). Differentiating, we get \( \frac{d}{dy}(u^2) = \frac{d}{dy}(2y + 1) \), which simplifies to \( 2u \frac{du}{dy} = 2 \). Solving for \( \frac{du}{dy} \) gives us \( du = \frac{1}{u} dy \), so \( dy = u \, du \).
03
Substitute in the Integral
Substitute \( u = \sqrt{2y+1} \) and \( dy = u \, du \) back into the integral. The original integral \( \int \frac{e^{\sqrt{2y+1}}}{\sqrt{2y+1}} \, dy \) becomes \( \int \frac{e^u}{u} \cdot u \, du \), which simplifies to \( \int e^u \, du \).
04
Integrate
The integral \( \int e^u \, du \) is straightforward, as the antiderivative of \( e^u \) is \( e^u \). Thus, we get \( e^u + C \), where \( C \) is the constant of integration.
05
Substitute Back to Original Variable
Express the result back in terms of \( y \). Since we let \( u = \sqrt{2y+1} \), substitute back to obtain \( e^{\sqrt{2y+1}} + C \) as the final answer for the original integral.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Substitution Method
The substitution method is a powerful tool in calculus, especially when dealing with complex integrals. It makes the integration process easier by transforming a complicated integral into a simpler one. In our problem, the inner function \( \sqrt{2y+1} \) is difficult to integrate directly. By letting \( u = \sqrt{2y+1} \), we simplify the expression. This method involves:
- Identifying an "inner function" \( g(y) \) as \( \sqrt{2y+1} \)
- Substituting \( u = g(y) \), converting \( dy \) in terms of \( du \)
- Transforming the integral to be in terms of \( u \) instead of \( y \)
Antiderivative
An antiderivative is simply the reverse of differentiation. It refers to a function whose derivative is the original function we started with. When you integrate a function, you are finding its antiderivative.For example, in our integral \( \int e^u \, du \), the antiderivative of \( e^u \) is known to be \( e^u \). The simplicity of the exponential function makes finding its antiderivative a direct operation. Remember, the process of finding an antiderivative involves:
- Recognizing the basic form of the function being integrated
- Using known antiderivatives, such as \( \int e^x \, dx = e^x + C \)
- Adding a constant \( C \) to express the general form of potential antiderivatives
Definite Integrals
Though our example involves an indefinite integral, it's helpful to understand definite integrals as well. A definite integral calculates the net area under a curve between specific limits. However, the technique of substitution can still apply to both indefinite and definite integrals.Definite integrals involve:
- Setting limits of integration on the variable \( y \)
- Transforming these limits to the new variable \( u \) once a substitution is made
- Computing the antiderivative as normal
- Plugging in the transformed limits to find the area