Functions Definition and 1000 Threads

  1. AN630078

    Composite and Inverse Functions Problem

    1. a. fg(x)=2(1/2(x-1))+1 fg(x)=2(x/2-1/2)+1 fg(x)=x-1+1 fg(x)=x gf(x)=1/2((2x+1)-1) gf(x)=1/2(2x+1-1) gf(x)=x+1/2-1/2 gf(x)=x The functions functions f(x) and g(x) are inverses of each other. This can be demonstarted by f(x)=2x+1 y=2x+1 x=2y+1 x-1=2y (x-1)/2=y Thus, y=1/2(x-1) = g(x) And...
  2. M

    Advanced functions (precalculus)

    This is my attempt so far: ##0.05=\frac{30t}{200000+t}## then I solved for t. And I got 333.88 min. I feel like this is way too simple of a solution and I didn't use all of what's given in the problem. For part 2 of the problem it asks, what happens to the concentration over time. I tried to...
  3. F

    I Asymptotes of Rational Functions....

    Hello, I know that functions can have or not asymptotes. Polynomials have none. In the case of a rational functions, if the numerator degree > denominator degree by one unit, the rational function will have a) one slant asymptote and b) NO horizontal asymptotes, c) possibly several vertical...
  4. banananaz

    MHB How do I find the Euclidean Coordinate Functions of a parametrized curve?

    I've been given a curve α parametrized by t : α (t) = (cos(t), t^2, 0) How would I go about finding the euclidean coordinate functions for this curve? I know how to find euclidean coord. fns. for a vector field, but I am a bit confused here. (Sorry about the formatting)
  5. srfriggen

    Comparing the domains of composite functions

    Hello, I have attached my question and the work. I believe the answer is correct. Looking for verification. Thank you!
  6. Sabertooth

    I Elliptic Function Rotation Problem

    Hi all:) In my recent exploration of Elliptic Function, Curves and Motion I have come upon a handy equation for creating orbital motion. Essentially I construct a trigonometric function and use the max distance to foci as the boundary for my motion on the x-plane. When I plot a point rotating...
  7. S

    I Convergence of sequences of functions with differing domains?

    Of the various notions of convergence for sequences of functions (e.g. pointwise, uniform, convergence in distribution, etc.) which of them can describe convergence of a sequence of functions that have different domains? For example, let ##F_n(x)## be defined by ##F_n(x) = 1 + h## where ##h...
  8. Sabertooth

    Expressing Elliptic Orbitals As Speed Functions.

    Hi everyone:) I have spend a couple of days trying to teach myself the math of orbital mechanics and have been able to generate a model of the orbital path of Haley's Comet, incorporating realistic distances and periods using Kepler's second law & ellipsoid functions. This is a GIF of the motion...
  9. M

    I Derivatives of Standard Functions

    I can't help but feeling these days that I don't actually understand where most of the maths I use comes from. Unfortunately, I can't remember whether this is due to the fact that I didn't take my studies seriously until the end of undergrad, or rather that these things were never actually...
  10. Riccardo Marinelli

    Initial condition of Wave functions with Yukawa Potential

    Hello, I was going to solve with a calculator the eigenvalues problem of the Schrödinger equation with Yukawa potential and I was thinking that the boundary conditions on the eigenfunctions could be the same as in the case of Coulomb potential because for r -> 0 the exponential term goes to 1...
  11. M

    MHB Sequence of functions : pointwise & uniform convergence

    Hey! 😊 Let $0<\alpha \in \mathbb{R}$ and $(f_n)_n$ be a sequence of functions defined on $[0, +\infty)$ by: \begin{equation*}f_n(x)=n^{\alpha}xe^{-nx}\end{equation*} - Show that $(f_n)$ converges pointwise on $[0,+\infty)$. For an integer $m>a$ we have that \begin{equation*}0 \leq...
  12. madafo3435

    I Differential analysis: convex functions

    I am reading A Course in Mathematical Analysis Volume 1 by D. J. H. Garling, and I am having trouble in the following demonstration of Section 2 Differentiation. part 4 of the test, the first part of the second inequality does not make sense, I do not understand its justification. I hoped they...
  13. xyz_1965

    MHB How do trigonometric functions and their inverses relate to each other?

    Take any trig function, say, arcsin (x). Why is the answer x when taking the inverse of sin (x)? Why does arcsin (sin x) = x? Can it be that trig functions and their inverse undo each other?
  14. xyz_1965

    MHB Is tan(x)^2 proper notation for the trig function tangent squared?

    Is tan^2 (x) the same as tan(x)^2? Note: I could have used any trig function. I know that tan^2 (x) means (tan x)^2. What does tan (x)^2 mean? Is it proper notation?
  15. Leo Liu

    I How did mathematicians discover the expressions of hyperbolic functions?

    The hyperbolic function ##\cosh t \text{ and } \sinh t## respectively represent the x and y coordinate of the parametric equation of the parabola ##x^2-y^2=1##. The exponential expressions of these hyperbolic functions are $$ \begin{cases} \sinh x = {e^x-e^{-x}} /2; \: x \in \mathbb R, \: f(x)...
  16. T

    What brain exercises improve brain functions based on facts

    Hi, there. I couldn't find much information about this on the net so I came here to ask if anyone here knows as I thought it would be the right forum or maybe I just wasn't looking hard enough. Please not that I don't mean skills but rather what actually works that improves brain functions like...
  17. anemone

    MHB Expressing First 1000 Positive Integers as Floor Functions

    How many of the first 1000 positive integers can be expressed in the form $\lfloor 2x \rfloor+\lfloor 4x \rfloor+\lfloor 6x \rfloor+\lfloor 8x \rfloor$, where $x$ is a real number?
  18. W

    Python Elementary Python Questions: Data Frames, k-nary functions

    Hi All, A couple of questions, please: 1) Say df is a dataframe in Python Pandas, and I select a specific column from df: Y=df[column].values. What kind of data structure is Y? 2) I want to find the sum of two numbers: Def Sum(a=0,b=0): return a+b If I want to find a sum over sum data...
  19. B

    A Jacobi Elliptic Functions and Integrals

    Are there any useful references or resources that intuitively show how Jacobi Elliptic functions [sn, cn, dn, etc] are geometrically interpreted from properties of ellipses? And how the Jacobi Elliptic functions and integrals can be shown to be generalizations of circular trig functions? Thanks!
  20. S

    Correct statement about composite and inverse functions

    f-1(f(A)) = A and f-1(f(B)) = B so options (a) and (c) are wrong. For (b), I get A ⊆ A For (d), I get B ⊆ B For (e), I get A ⊆ A So there are three correct statements? Thanks
  21. chwala

    Transformation of trigonometry functions

    kindly note that this solution is NOT my original working. The problem was solved by my colleague. I have doubts with the ##k## value found. Is it not supposed to be ##k=0.5?## as opposed to ##k=2?##. From my reading on scaling, the graph shrinks when ##k## is greater than ##1## and conversely.
  22. Math Amateur

    MHB Lebesgue Integration of Simple Functions .... Lindstrom, Lemma 7.4.6 .... ....

    I am reading Tom L. Lindstrom's book: Spaces: An Introduction to Real Analysis ... and I am focused on Chapter 7: Measure and Integration ... I need help with the proof of Lemma 7.4.6 ... Lemma 7.4.6 and its proof read as follows: In the above proof by Lindstrom we read the following: " ...
  23. Math Amateur

    I Lebesgue Integration of Simple Functions .... Lindstrom, Lemma 7.4.6 ...

    I am reading Tom L. Lindstrom's book: Spaces: An Introduction to Real Analysis ... and I am focused on Chapter 7: Measure and Integration ... I need help with the proof of Lemma 7.4.6 ... Lemma 7.4.6 and its proof read as follows: In the above proof by Lindstrom we read the following: " ...
  24. Math Amateur

    MHB Measurable Functions .... Lindstrom, Proposition 7.3.7 .... ....

    I am reading Tom L. Lindstrom's book: Spaces: An Introduction to Real Analysis ... and I am focused on Chapter 7: Measure and Integration ... I need help with the proof of Proposition 7.3.7 ... Proposition 7.3.7 and its proof read as follows: In the above proof by Lindstrom we read the...
  25. Math Amateur

    I Measurable Functions .... Lindstrom, Proposition 7.3.7 .... ....

    I am reading Tom L. Lindstrom's book: Spaces: An Introduction to Real Analysis ... and I am focused on Chapter 7: Measure and Integration ... I need help with the proof of Proposition 7.3.7 ... Proposition 7.3.7 and its proof read as follows: In the above proof by Lindstrom we read the...
  26. J

    MHB Exponential functions (calculator exercise)

    Hi there, I have tried to do these questions but I don't understand. Any help would be appreciated!
  27. B

    Calculus 1 problems: functions, integrals, series

    Mentor note: Moved from technical section, so is missing the homework template. Im doing some older exams that my professor has provided, but I haven't got the solutions for these. Can someone help confirm that the solutions I've arrived at are correct?
  28. H

    B What Are the Sign Rules for Second Degree Functions?

    judge whether the following expressions are larger than, smaller than or equal to zero i) a+b+c ii)a-b+c iii)4a+2b+c iv)c-e I know that <0, b> 0, c> 0, d> 0 and e <0 but I don't know what to do
  29. Leo Liu

    Understanding Probability Density Functions and Their Properties

    My questions are as follows: 1. How do we find them and why do we need them? 2. What are the meanings of the mean and the median of a PDF? Are the formulae below correct? $$\int_{a}^{median} f(x) \mathrm{d}x = \int_{median}^{b} f(x) \mathrm{d}x$$ $$\int_{a}^{mean} f(x) \cdot x \mathrm{d}x =...
  30. N

    Why should arguments of certain functions be dimensionless?

    This is my approach: These quantities namely mass, length, and time, are all additive in nature. ##2 m + 3m = 5 m ##. If the argument of the functions mentioned in the problem statement is not dimensionless, then mass, length or time do not remain additive in the image space of the functions...
  31. T

    MHB Derivatives with Quadratic Functions.

    Slightly confused at what it wants me to do here?
  32. O

    I Rotate Functions with Derivatives: A Quantum Mechanics Homework

    I was solving a problem for my quantum mechanics homework, and was therefore browsing in the internet for further information. Then I stumbled upon this here: R is the rotation operator, δφ an infinitesimal angle and Ψ is the wave function. I know that it is able to rotate a curve, vector...
  33. agnimusayoti

    Absolute value of trigonometric functions of a complex number

    So far I've got the real part and imaginary part of this complex number. Assume: ##z=\sin (x+iy)##, then 1. Real part: ##\sin x \cosh y## 2. Imaginary part: ##\cos x \sinh y## If I use the absolute value formula, I got ##|z|=\sqrt{\sin^2 {x}.\cosh^2 {y}+\cos^2 {x}.\sinh^2 {y} }## How to...
  34. H

    Find the number of possible functions from one set to another

    I have tried to solve them. I would like to know if my answers are correct. (a) The total number of functions without any restrictions ##=n^m## The number of functions such that ##f(x)## is never ##1## ##=(n-1)^m## The number of functions such that ##f(x)=1## for at least one ##x\in S_m##...
  35. E

    B Tangents to a curve as functions of different variables

    Let's say we have a curve in 2D space that we can represent in both cartesian and polar coordinates, i.e. ##y = y(x)## and ##r = r(\theta)##. If you want the tangent at any point ##(x,y) = (a,b)## on the curve you can just do the first order Taylor expansion at that point $$y(x) = y'(a)x +...
  36. Physics lover

    No. of positive integral solutions of fractional functions

    I know how to find integral solutions of linear equations like x+y=C or x+y+z=C where C is a constant. But I don't have any idea how to solve these type of questions.I am only able to predict that both x and y will be greater than 243554.Please help.
  37. Physics lover

    No. of solutions of an equation involving a defined function

    Here is a pic of question My attempt-: I defined functions f(x-1) and f(x+1) using f(x).After defining them,I substituted their values in the equation f(x-1)+f(x+1)=sinA. For different ranges of x,I got different equations. For 1<x<2,I got 1-x=sinA. But now I am confused.For each different...
  38. anemone

    MHB Inequality of cubic and exponential functions

    Prove that $3^n\ge(n+3)^3$ for any natural number $n\ge6$.
  39. E

    B Difference between functions and variables

    This is probably a silly question, though it's confused me a little so I thought I'd ask. It is my understanding that a function is loosely defined as a mapping between two sets, whilst a variable can represent an element of either of those sets. I'll take the example of velocity, since it's...
  40. A

    Medical Text about higher cognitive functions of the brain?

    I'm looking for a document (possibly online) which describes the higher cognitive functions (such as thinking, planning, creativity, comprehension, reasoning, etc.) from the neuroscientific point of view. I found only texts of brain anatomy or other describing senso-motoric and metabolic aspects...
  41. S

    I Rewriting a piecewise function using step functions

    Suppose we have a piecewise function f(t) = exp(c*t) when 0 <= t < 2 and f(t) = 0 when t >= 2. Can the above be rewritten as f(t)= exp(at)*[H(t-0) - H(t-2)], H is a heaviside function.
  42. M

    MHB Show that the two functions are identical

    Hey! :o For the functions $f:A\rightarrow B$, $g:B\rightarrow A$ and $h:B\rightarrow A$ it holds that $(g\circ f)(x)=x, \ \forall x\in A$ and $(f\circ h)(x)=x, \ \forall x\in B$. Show that it holds that $g\equiv h$. I don't really have an idea how to show that. Let $x\in A$. Then $(g\circ...
  43. V

    A How to work with expanded functions?

    I solve problem where I use functions which are expanded upto some order. I multiply them, make square root and make derivatives or solve differential equations. What is the right way to deal with such problem? Shall I expand all functions after every step or work with unexpanded functions and...
  44. M

    Engineering Parseval's Theorem - Average Power of the difference of functions

    Hi, So I have a quick conceptual question about Parseval's theorem in this application. In previous parts of this question, we have found the average powers of both f(t) and g(t) by integration and using the complex Fourier series respectively (not sure if this is relevant to my question)...
  45. Mounice

    Solving Potential of a Charge Outside a Sphere with Green Functions

    I was wondering if there is a way to deduce the solution of the potential of a charge outside a sphere given by the image method, though Green functions. Because of a Dirichlet condition (GD(R,r')=0), I know that a solution can be written as GD=Go+L, where ∇2L=0. But in order to approach this...
  46. P

    Partial derivatives of thermodynamic state functions

    I'm in a first-year grad course on statistical mechanics and something about multivariable functions that has confused me since undergrad keeps popping up, mostly in the context of thermodynamics. Any insight would be much appreciated! This is a general question, but as an example imagine...
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