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  1. Mark44

    I think this sentence in a children's book is grammatically incorrect

    You're right -- the "will be equal to ..." part threw me off. I should have said that "will be equal to more than" is equivalent to "will be more than," which, in addition, is less obfuscating.
  2. Mark44

    I think this sentence in a children's book is grammatically incorrect

    I see your point. This is a somewhat clumsy way to say "is at least." We could say that 2 + 4 "is at least" 5.
  3. Mark44

    I think this sentence in a children's book is grammatically incorrect

    "Bolded" and "emboldened" have different meanings, with "bolded" usually used in the context of printed text, and "emboldened" usually used to describe an emotional state. I have bolded the preceding text. I was at first fearful, but became emboldened to write this reply to your post.
  4. Mark44

    How to Use a Multidimensional Array to SED?

    The array in the input file has 9 rows, each with two numbers. The for loop in your code runs 10 times. See if changing the condition part of your loop from i <= 9 to i < 9 fixes your problem.
  5. Mark44

    How to verify the points

    Thread locked. Your image files can't be viewed without logging into another site. Please start a new thread with any images attached in your work, not as links to external sites.
  6. Mark44

    What's the point of having a dress code stricter than business casual?

    As a tourniquet, perhaps? Or for those annoying sucking chest wounds, you can just wad it up and stuff it in there.
  7. Mark44

    Programs What programs can I apply to ?

    It would have helped if you had mentioned right away, that the "local college" was not one in the US. From post #5:
  8. Mark44

    Visual C++ array question

    Here's a different approach from the one presented by @wle, that uses the idea hinted at by @Klystron. This code will fill the array with 0000, 0001, 0002, ... , 7777. Nested loops aren't ideal for performance, as they cause the CPU pipeline to be invalidated, but I don't think this is a concern...
  9. Mark44

    Python Finding the day from a given date

    Given that the OP asked about an interview problem, this is probably good enough, but this algorithm suffers from not calculating leap days correctly (e.g., the rule is different in centuries that are divisible by 100 vs. those that are divisible by 400). It is also problematic in doing...
  10. Mark44

    I How to integrate with functions of differentials?

    Yes, that is more-or-less correct. The expression ##\frac{d(\tan(x))}{dx}## is the derivative of the tangent function, with respect to its variable x. The substitution was ##u = \tan(x)## from which the differentials of the two sides would be as you have below. Note that we would usually write...
  11. Mark44

    What's the point of having a dress code stricter than business casual?

    "Other than that, Mrs. Lincoln, how was the play?"
  12. Mark44

    Slope of a line

    No. Are you just guessing? Do you know the formula for calculating the slope of the line between two points? In your first post in this thread you wrote: That is not the formula for the slope of a line.
  13. Mark44

    Slope of a line

    I said I got a number less than 1. From your graph, it appears that the points you're using are (-2, -1) and (3, 2). You have labeled this points, but the image is too poor for me to read them -- I just counted squares on the grid. If you know two points on a line, how do you find the slope of...
  14. Mark44

    Comp Sci Induction Proof for all strings: Can't understand the Question

    Our life, and yours, would have become easier if you had explained what ##t^n## means right at the beginning of this thread. I realize that English is not your first language. To concatenate two strings means that the two strings are joined together to form a single string. For example, the...
  15. Mark44

    Slope of a line

    Are you asking about problem 5? If so, your answer is wrong. For the two points you marked, what is the rise (vertical change) and what is the run (horizontal run)? I get a slope that is less than 1. In the future, if you post an image, please make more of an effort to post a legible picture...
  16. Mark44

    Trig Equation 2tanx= 1/2tan2x

    Please use parentheses. In the first equation, 1/2tan2x means ##\frac 1 2 \tan(2x)##. If you don't use LaTeX, it should be written as 1/(2 tan(2x)). In the second equation, what you wrote on the right side means ##\frac{2\tan(x)}1 - \tan^2(x)##, which is probably not what you meant. As inline...
  17. Mark44

    Comp Sci Induction Proof for all strings: Can't understand the Question

    @zak100, you will never be able to do this problem if you can't answer the question @QuantumQuest asked way back in post #2. His hint that ##t^n## represents the concatenation of a string t with itself some number of times seems to be the best interpretation of this notation.
  18. Mark44

    Finding values for a and b for this polynomial

    No, it means that (5, 0) is on the curve. The rest of the hint is fine.
  19. Mark44

    Comp Sci Induction Proof for all strings: Can't understand the Question

    Well, this is exactly what you need to prove. Of course you can't -- you can't use something that you're supposed to prove. Take a look again at what I wrote in post #10:
  20. Mark44

    I Numerical ODE Fail

    ODE45 and NDSolve don't know anything about the analytic solution. All they have to go on are the differential equation and initial conditions, and they use this information to get another solution point. The farther away you get from, in this case, t = 0, the less accurate the computed solution is.
  21. Mark44

    I Numerical ODE Fail

    See post #9. From the documentation for the method you're using. They should give you some idea of the accuracy of the method in terms of the interval around the initial conditions.
  22. Mark44

    Help with L'Hôpital's rule

    Differentiability isn't necessary. If both limits on the right side of the equation I wrote exist, and the limit in the denominator is not zero, then the quotient of the limits equals the limit of the quotients.
  23. Mark44

    I Numerical ODE Fail

    I don't do Mathematica, but there are a couple of things in your screen shot that puzzle me. First, when you define the exact solution, xE[t_], you have a different parameter in the definition: $$xE[t_\ ] := \frac{Tanh[b + \frac t {\sqrt 2}]}{\sqrt{-\alpha \epsilon}}$$ Shouldn't you have t_ on...
  24. Mark44

    I Numerical ODE Fail

    Numerical solutions don't necessarily give good solutions over a large interval. Your numeric solution matches the exact solution pretty well when x is close to 0, the value used in the initial conditions. When x is relatively far away from 0, the numeric solution varies considerably from the...
  25. Mark44

    Comp Sci Induction Proof for all strings: Can't understand the Question

    I don't think so. ##t^n## probably represents a string with n characters, and ##|t^n|## might mean the length of such a string. Since you aren't sure, you better make sure that's the case. I would start with a base case of n = 1, a string that contains one character. This is the Induction...
  26. Mark44

    I Trouble with infinity and complex numbers

    I thought that might be it.
  27. Mark44

    Python To print two equal sized 2-D arrays adjacently in a single .txt file

    I don't believe there is a numpy (or scipy) function named either npsavetext or .npsavetext. There is a function named savetext(), but it is limited to saving a single one- or two-dimension array to a text file. Based on the documentation I found...
  28. Mark44

    I Trouble with infinity and complex numbers

    Is this really what you meant? For a function ##f : \mathbb C \to \mathbb C##? You have an extra two dimensions. For the domain you need only two dimensions, not four.
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