Recent content by lxman

  1. L

    A question about the speed of EM and mechanical waves

    I have known for many years that the speed of sound (usually quoted ≈340 m/s) and the speed of light (usually quoted ≈3*10^8 m/s) are vastly different. Doing some reading, I would seem to conclude that part of the reason for this is the fact that sound is a mechanical wave, propagated through...
  2. L

    Electrical stability of an atom

    Alright then, let's see . . . eV is a unit of energy. Therefore would I be correct in concluding that the CO molecule has a quantity of energy closer to zero and therefore it would be more electrically stable?
  3. L

    Electrical stability of an atom

    Homework Statement As shown in class the electric potential energy of a water molecule is -5.33 eV. Which molecule is more electrically stable, H2O or CO? Why? Homework Equations EPE=Kc*q1*q2/r12 The Attempt at a Solution The water molecule's EPE is -5.33 eV. The carbon...
  4. L

    Determining the interval of convergence

    Okay, [0,14] did the trick. Thanks for hanging in there with me. I have a couple of questions still left. First off, the inclusion of zero in the set. The way that I am seeing it, the coefficients themselves make up a series which is alternating and decreasing (actually beginning with term...
  5. L

    Determining the interval of convergence

    Okay, I'm definitely not questioning you. Let me start from scratch with the problem definition directly from the homework and maybe I missed something or left something out. Represent the function f(x)=x^0.4 as a power series: \sum^{\infty}_{n=0}c_{n}(x-7)^{n} Find the following...
  6. L

    Determining the interval of convergence

    Hmm, thanks much for the help, but I tried giving that to my professor and he says "not correct." I thought it would be (6,8], but just in case I was wrong, I tried [6,8], [6,8) and (6,8). He's not agreeing with any of them. I thought I understood things all the way, but I'm confused again.
  7. L

    Determining the interval of convergence

    Nope, that should be: \left|\frac{1}{x-7}\right|<1 which tells me x>8 or x<6
  8. L

    Determining the interval of convergence

    Okay, so looking at what I have to work with, I can calculate that: \frac{a_{n+1}\ (x-7)^{.4-n-1}}{a_{n}\ 7^{.4-n}}=\frac{.4-n}{n+1}\ (x-7) Now, the ratio test is looking at \lim_{n\rightarrow\infty} which would be x-7. Therefore, I need \left|x-7\right|<1\Rightarrow 6<x<8, and I still...
  9. L

    Determining the interval of convergence

    Okay, that makes good sense. I have to define a center since depending on where I pick the center, the curve will be different and the interval of convergence will be different. So, my center is 7 in this case. What I understand from what you have written is that each successive numerator...
  10. L

    Determining the interval of convergence

    Homework Statement f(x)=x^{0.4} Construct a power series to represent the function and determine the first few coefficients. Then determine the interval of convergence. The Attempt at a Solution Determining the first few coefficients is simple enough. Take the first few...
  11. L

    Estimating integral with Maclaurin series

    Thank you all for your help.
  12. L

    Estimating integral with Maclaurin series

    Okay, yep, missed that one completely. Integrating gives me: \frac{7x^{3}}{3}-\frac{49x^{7}}{6} Now, plugging in 0.77, I get -0.245385 which is much closer. Again, I presume the error is from only using two terms.
  13. L

    Estimating integral with Maclaurin series

    SammyS, your idea sounds MUCH simpler, but you would have to explain the details of implementation to me. So, doing it the hard way - and yes, it gets a bit messy, so I won't post all the details. I end up with the first two non-zero terms being term 2, which evaluates to 14, and term 6, which...
  14. L

    Estimating integral with Maclaurin series

    The original problem statement says to use the first two terms of the Maclaurin series. So when I am constructing the series, I just basically throw away any terms with zero values, and the non-zero terms then become my series. Is this correct?
  15. L

    Estimating integral with Maclaurin series

    Homework Statement Assume that sin(x) equals its Maclaurin series for all x. Use the first two terms of the Maclaurin series for sin(7x^2) to approximate the integral: \int_{0}^{0.77}sin(7x^{2})\ dx The Attempt at a Solution If I understand correctly, a Maclaurin series is just a...
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