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MermaidWonders
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Suppose that $\int_{-\infty}^{\infty} f(x)\,dx$ converges. Then $\lim_{{x}\to{-\infty}}f(x) = \lim_{{x}\to{\infty}}f(x)$. Why is it true? I have some trouble understanding this intuitively.
MermaidWonders said:Suppose that $\int_{-\infty}^{\infty} f(x)\,dx$ converges. Then $\lim_{{x}\to{-\infty}}f(x) = \lim_{{x}\to{\infty}}f(x)$. Why is it true? I have some trouble understanding this intuitively.
MermaidWonders said:Oh, OK, but why can't the limit equal to any other number other than 0 for it to converge?
MermaidWonders said:What's $\varepsilon$ and $a$? Do these variables pertain to the precise definition of a limit? If so, this is something we haven't touched on yet, so would you mind explaining their significance with respect to this question? Also, is there another way to approach this question using the regular/basic definition of limits? Thanks!
MermaidWonders said:Oh, oops. By "regular/basic definition" of limits, I meant like limits of the basic form $\lim_{{x}\to{a}}f(x)$... And yeah, the generic definition of the limit you have up there is unfamiliar to me too, but I do suppose we'll learn it later.
MermaidWonders said:Yeah, sure. I'll just plant this "rule" into my brain for now and then see if I can understand it conceptually once we do learn more about limits. But for now, is possible for you to draw a picture to illustrate why the limit has to equal to 0 and not any other constants? That's what I'm still having trouble with.
MermaidWonders said:Oh, OK, but why can't the limit equal to any other number other than 0 for it to converge?
MermaidWonders said:Oh, so that's it? Then does it mean that $\lim_{{x}\to{-\infty}}f(x)$ would also have to approach 0 in order for the integral to converge during the entire stretch of the interval from $-\infty$ to $\infty$?
It diverges? Since the area under the "curve" tends towards infinity as the upper limit of integration is $\infty$.greg1313 said:Another way of looking at this is to visualize $\int_0^\infty c\,dx$, where $c>0$. Now make a drawing, including the $x$-axis, of what this integral looks like in terms of an area between $c$ and the $x$-axis. What do you notice?
MermaidWonders said:It diverges? Since the area under the "curve" tends towards infinity as the upper limit of integration is $\infty$.
Understanding convergence in integrals and limits is important for accurately calculating the values of integrals and limits, which are essential in many areas of mathematics and science. Additionally, understanding convergence helps to ensure the validity and accuracy of mathematical models and equations.
To intuitively understand convergence, it is helpful to think of it as the process of approaching a certain value or limit as the input or variable gets closer to a specific value. In integrals, convergence is achieved when the upper and lower limits of integration approach a specific value and the resulting area under the curve approaches a finite value.
Some common tests for convergence in integrals include the comparison test, the limit comparison test, the ratio test, and the integral test. In limits, common tests for convergence include the squeeze theorem, the limit comparison test, and the ratio test.
One common misconception is that a series or integral must approach a specific value in order to converge, when in reality, it may converge to a range of values. Another misconception is that a series or integral must approach a certain value at a certain rate, when in reality, it may approach the value at a slower or faster rate depending on the specific convergence test used.
Checking for convergence is important because it ensures the accuracy and validity of mathematical calculations. Inaccurate calculations can lead to incorrect conclusions and flawed mathematical models, which can have significant consequences in various fields such as physics, engineering, and economics.