Exponential Definition and 1000 Threads

  1. J

    Lagrangian of three bodies, using an exponential potential

    What I know: L = T - V V = e^(x1-x2) + e^(x2-x3) for n = 3 and a mass = 1 What I believe: T = .5Ʃ (x'_i)^2 from 1 to n So let's say you have three bodys that can just be considered pints masses of 1 and on the same line: x1 x2 x3 They have an...
  2. G

    MHB Integral Notation of an exponential Brownian motion

    Good day! I am reading the paper of Marc Yor (www.jstor.org/stable/1427477). equation (1.a) seems unfamiliar to me since the $ds$ comes first before the exponential part; $$ \int_0^t ds \exp(aB_s + bs). $$ Can you please help me clarify if there is a difference with the above notation as...
  3. N

    GCD & LCM of 6 Integers: Exponential Form

    Homework Statement What is the greatest common divisor and least common multiple of the integers below (answer should be left in exponential form)? 2^{3}, 3^{3}, 5^{1}, 11^{2}, 13^{3} and 2^{1}3^{3}5^{2}7^{4}13^{1}Homework Equations The Attempt at a Solution This is exactly the way the...
  4. R

    Integrals and exponential growth problem

    Homework Statement Before the AP exam Cal Q Luss has 3 hours to cram: during this time, he wants to memorize a set of 60 derivative/integral formulas. According to psychologists, the rate at which a person can memorize a set of facts is proportional to the number of facts remaining to be...
  5. A

    Minimum of two iid exponential distributions

    Let X_1, X_2 \sim Exp(\mu) and Y = min(X_1, X_2) then find E[Y]. My attempt is as follows: $$E[Y] = E[Y/X_1<X_2]P(X_1<X_2) + E[Y/X_1>X_2]P(X_1>X_2) \\ = \frac{1}{2} (E[X_1/X_1<X_2] + E[X_2/X_1>X_2] ) \\ = \frac{1}{2} (1/\mu + 1/\mu) \\ = 1/\mu$$ But, we know that minimum of two exponentially...
  6. V

    Calculate exponential growth when rate r is changing

    The formula f(t) = I(1 + r)t gives the value of something after it has grown for t years, at rate r, with an initial value I. What if the growth rate r is continuously increasing? What is the formula now? Does it relate somehow to xx?
  7. M

    Exponential fourier series expansion

    Hey, thanks for taking the time to look ay my post (: I have attached a file which shows the question I am stuck on, and my attempt at working it out. My problem is the answer I get, is different to what my Lecturer gets (shown in the attachment). He worked it out a different way to me, he...
  8. D

    Is g(x)=5^sqrt(x) an Exponential Function?

    Our textbook defines an exponential function as f(x) = ab^x. However, a question was brought up about a function, g(x) = 5^sqrt(x). Is g an exponential function? It looks like an exponential graph for x>0, but is not continuous on R. Thanks in advance!
  9. 6

    Assigning exponential weights depending upon sample size

    I'm trying to find a function which will assign exponential weights depending upon sample size. nu=an equally space coefficient sequence (.05,..,.5; by=.05). m=sample size (10 in this case) Adding each observation in nu, implies a weight of 1, which makes the sum of weights m. I need...
  10. S

    PDF of an exponential distribution

    Homework Statement Hi! I'm trying to find the PDF of W = abs(X-λ), where X is an exponential R.V. with rate parameter λ>0. Homework Equations The PDF for an exponential distribution is ∫λe^(-λx)dx. Taking the derivative of a CDF will yield the PDF for that function (I'm aware there are...
  11. A

    MHB Simplifying exponential expressions

    Simplify 8p-3 x (4p2)-2/p-5. This is what I got: First thing I did was flip everything to get rid of the negative exponents: p5/8p3x(4p2)2 next thing I did was multiply the 4p2 by 2 p5/ 8p3x16p4Then I subtracted thep5 from the 8p3 p2/8x16p4 and ended up with 1/128p2 I know that the...
  12. D

    Proving the memoryless property of the exponential distribution

    Given that a random variable X follows an Exponential Distribution with paramater β, how would you prove the memoryless property? That is, that P(X ≤ a + b|X > a) = P(X ≤ b) The only step I can really think of doing is rewriting the left side as [P((X ≤ a + b) ^ (X > a))]/P(X > a). Where...
  13. QuestForInsight

    MHB Prove Exponential Limit: $$e^{x/2}$$

    Show that $$ \lim_{n \to \infty} \prod_{1 \le k \le n}\left(1+\frac{kx}{n^2}\right) = e^{x/2}$$
  14. F

    How to Solve the Complex Equation zn-1=\bar{z}?

    Hi I have come across this equation: zn-1=\bar{z}, z\inℂ* (ℂ*:=ℂ\0ℂ) There are numerous obvious equalities that can be used, but I don't seem to reach a satisfying final answer. Any help would be appriciated. Thanks in advance :)
  15. nukeman

    Easy exponential question-> 1/3(8)^(-2/3)

    Easy exponential question---> 1/3(8)^(-2/3) Homework Statement I am doing a linear approximation question, and got stuck here with this simple stuff. 1/3(8)^(-2/3) Can anyone explain what I need to do to turn the above into 1/12 ? Homework Equations The Attempt at a...
  16. A

    Trigonometric function and complex exponential

    1. Homework Statement - multiplication of trigonometric function and complex exponential 2. Homework Equations the question is, Akcos(ωt) × e-jωt 3. The Attempt at a Solution it is, Ak/2 + (Ak/2)e-j2ωt ? by using cos(ωt) = 1/2ejωt + 1/2e-jωt
  17. S

    Exponential Inequality Challenge: Simplify and Solve for x

    Homework Statement (5 + √24)x + (5 - √24)x > 98 Homework Equations inequalities exponential The Attempt at a Solution I don't know how to start...trying to put log to both sides could not take me anywhere because the LHS can't be simplified...
  18. D

    Why is the Exponential Constant e Unitless?

    Is there a reason why e doesn't have units attached? I've kind of just accepted it but was wondering the reason behind it.
  19. M

    Some trigonometric, exponential thing?

    How can we say: f(x)=A'sin(kx)+B'cos(kx) or equivalently f(x)=Ae^{ikx}+Be^{-ikx}?? How are these two equivalent knowing that e^{ix}=cosx+isinx I don't get this?
  20. A

    Exponential distribution/hydra population

    Hi, Somebody asked me for some help with his calc II homework, and this was one of the questions: "A hydra is a small freshwater animal and studies have shown that its probability of dying does not increase with the passage of time. The lack of influence of age on mortality rates for this...
  21. J

    [Complex exponential] Solutions must be wrong

    Homework Statement Hi, I would like to get feedback if my z-plot is accurate for the following complex exponentiala: a=2*exp(j*∏*t) b=2*exp(j*∏*-1.25) c=1*exp(j*∏*t) d=-j*exp(j*∏*t) Further analysis: a= -2 because cos(∏) = -1 and sin(∏)=0 b= actual complex number A*cos(∅)+j*sin(∅) c= -1...
  22. C

    Limits of derivatives of an exponential

    Homework Statement Determine the lowest derivative order for which the limit towards 0+ of the nth order derivative of f is nonzero (or otherwise does not exist). f = e^{\frac{-1}{x^{2}}} Homework Equations lim_{x\rightarrow0+}\frac{d^{n}}{dx^{n}}e^{\frac{-1}{x^{2}}} The Attempt at...
  23. L

    HELP to solve an exponential equation with one unknown

    Hi, I have an equation with one unknown. This is the 'B' in the equation. I need to solve for 'B'. Can you help me to rearrange this complex equation to solve for B in terms of everything else please? =(() - (DCRMgAl)) ∗ ^(−∗(()+()))+ ((DCRMgAl )- (DCRAl ))∗ ^(−∗∗() )+((Al) - (DCRMg)) ∗...
  24. phosgene

    Finding the value of an exponential given that e^a=10 and e^b=4

    Homework Statement Suppose that e^a=10 and e^b=4. Find the value of loga(b) Homework Equations ln(b)=loga(b)/loga(e) The Attempt at a Solution So far I've only gotten to the above equation rearranged to: ln(b) loga(e)=loga(b)/. I'm unsure as to where I'm supposed to go...
  25. C

    How Do You Invert the Function Q(t) in a Camera Flash Capacitor Model?

    Homework Statement When a camera flashes, the batteries begin recharging the flash capacitor which stores the charge Q according to the function Q(t) = Q* (1-e-t/a) where t is the elapsed time in seconds since the camera flash and Q* and a are non-zero (a) What does Q* represent? (b) Find the...
  26. S

    Transformations of exponential functions

    Homework Statement Im not sure what each of the variables do in y=cax-p +q Homework Equations The Attempt at a Solution my understanding is that -q is for vertical shifts/transformations -p is for horizontal shifts/transformations -and c is for vertical stretching not...
  27. G

    Understanding Nonlinear Exponential Maps for Vector Fields

    I'm having trouble understanding the exponential map for nonlinear vector fields. If dσ/dt=X(σ) for vector field X, then how does one interpret the solution: σ(t)=exp[tX]σ(0) ? If X is nonlinear, then X is not a matrix, so this expression wouldn't make sense. If X is a...
  28. G

    MHB Solve Exponential: Division w/ln - Answer Not Found

    How do you divide using ln: my example is x(7ln5-ln3)=-2ln5 and divide 7ln5-ln3 by both side to get x. So I have -2ln5/7ln5-ln3 and I can't seem to find the answer.
  29. P

    Exponential Derivative problem

    Homework Statement dy/dθ =2·3^(−θ) Homework Equations The Attempt at a Solution 2*(d/dθ)(3^(-θ) 2(3^(-θ)ln(3)) (2ln(3))/(3^θ) I keep getting this wrong and I'm not sure why. Could someone point out my mistake?
  30. M

    Particular Integral of Exponential

    First-Order Linear System Transient Response Hey there, I am trying to solve a problem of first order equation which is A temperature sensor has a first order response with τ = 18 seconds. The calibration curve of the sensor is presented in Figure 1. Graph the sensor response when it is...
  31. C

    Help with income raise problem, possible exponential problem?

    Homework Statement Hi, This is probably an easy equation and I know this is the pre-cal section and this is for my engineering math class but I feel like people in a pre-cal forum should be able to help! I'm writing an essay for my engineering math class and I am trying to calculate the income...
  32. L

    Complex exponential expressions.

    Homework Statement I just need some kind of explanation in layman's terms of what exactly is going on here. It seems as though I am missing some key element from trig. I am in a Signals class and the book lacks an explanation of the reduction used and ultimately why. Homework...
  33. M

    Rationale Behind Writing Exponential Terms in Ch. 1 Eq. 38

    Dear PF users What is the rationale for Sze to write the exponential terms in ch. 1, Eq. 38 once as \exp \left[ -\frac{E_C - E_F}{kT} \right] and once as \exp \left[ \frac{E_F - E_D}{kT} \right] ? In both cases E_F is larger than either E_C or E_D. To me, for the sake of not having to worry...
  34. T

    Question about exponential decay timing.

    I'm trying to understand the concept of exponential decay. To clarify, the decay of Uranium is not the same as say pulling the plug in a tub full of water. The water will drain out of a tub at a steady rate from start to finish. I assume Uranium doesn't do that. So you COULD say the water has a...
  35. P

    Very simple exponential function quesiton

    The derivative of e^(2x): let y = e^(2x), let u = 2x, so y = e^u chain rule: du/dx * dy/du = 2*e^u = 2e^u = 2e^(2x) this is the solution copied from my book, my question is why do they let u = 2x? is e^u the same as e^x? If so then wouldn't all derivatives of the exponential functions be in...
  36. O

    Find Exponential Equation from data points

    Hi guys I'm helping my girlfriend with her Calc 1 homework and we seem to be stuck on this one problem. Am I missing something obvious? Homework Statement Homework Equations P = P_0 a^t \frac{5}{20} = \frac{P_0 a^1}{P_0 a^{-1}} \frac{1}{4} = a^2 a =...
  37. J

    Exponential distribution problem

    Hello forum, I recently lost my notes on this matter, so I hope someone can fill in the gaps in my memory. The problem I am working on is the following: For one ticket window, the waiting time for one people satisfies an exponential distribution λe-λt and expected waiting time is 4 min...
  38. D

    WHY? is the relationship between speed and time exponential?

    WHY!? is the relationship between speed and time exponential? I am actually a finance major but I like to learn about physics on my spare time. One of the more fundamental concepts I am having a hard time understanding is why the relationship between speed and time is exponential. Can someone...
  39. K

    Understanding Exponential of Operator: Expansion and Eigenvalues Explained

    Hi there, I learn from the text that the exponential of an operator could be expanded with a series such that e^{\hat{A}} = \sum_{n=0}^{\infty} \frac{\hat{A}^n}{n!} So if the eigenvalue of the operator \hat{A} is given as a_i e^{\hat{A}}|\psi\rangle will be a matrix with diagonal elements...
  40. A

    Spivak - Radioactivity and the Exponential Function

    Homework Statement A radioactive substance diminishes at a rate proportional to the amount present (since all atoms have equal probability of disintegrating, ...). If A(t) is the amount at time t, this means that A'(t)= p * A(t) for some p representing the probability that an atom will...
  41. B

    Derivative of Exponential Function

    I am reading the about the derivative of an exponential function using the limit definition, but one step I don't quite understand: lim_{h\rightarrow0}\frac{a^h -1}{h} = f'(0) Wouldn't that limit equal 0/0?
  42. T

    Solution of exponential equation

    How does the given equation: βe^(x/β)-x = β+(A/B) solves to x = √(2A/βB) when β is large?
  43. Y

    Derivative of the exponential function with base e

    For an exponential function of the form y=a^x First derivative , d/dx [a^x ] = a^x∙ lim┬(δx→0)⁡{(a^δx-a^0)/δx} = a^x∙ m_((0,1)) now if m_((0,1)) which is the gradient of the y-axis intersection point of the exponential function equal to 1 exactly...
  44. C

    Exponential function differentiation

    if first derivative is the slop of the given functions, then what is the physical meaning of exponential function remaining the same function after differentiation?? does it mean its vertical tangency make it indifferentiable? please clarify me the concept... regards
  45. W

    Sum of the Values of X, Exponential Equation

    Homework Statement (4x)^(1 + log(base 2) (x)) = 8(x^3) What is the sum of the values of x that fullfill that equation? A) 2.5 B) 2.0 C) 1.5 D) 1.0 E) 0.5Homework Equations Use the exponential equation only and make the lower one (exponented) 1.The Attempt at a Solution (4x) = (2 x^(1/2))^2...
  46. A

    Dividing with exponential functions

    Homework Statement When attempting to divide the following equality (a "tangency condition" in microeconomic consumer theory), I'm puzzled by the solution derived here, please explain the procedure for arriving at the solution. Many thanks! Homework Equations I differentiated the...
  47. H

    Linear control ODE - exponential convergence?

    Hello, I'm having hard times with the following simple linear ODE coming from a control problem: $$u(t)' \leq \alpha(t) - u(t)\,,\quad u(0) = u_0 > 0$$ with a given smooth α(t) satisfying $$0 \leq \alpha(t) \leq u(t) \quad\mbox{for all } t\geq 0.$$ My intuition is that $$\lim_{t\to\infty}...
  48. M

    How does the exponential function work?

    How does the exponential function work
  49. P

    Exponential decay, but results reach 0

    So I have a situation where the results in a table (x and y), where y reaches 0. According to my understanding, mathematically, exponential decay can never reach 0, right? So does that mean that I can't use an exponential curve of best fit with the results in my table (x = 0,1,2,3), (y = 4...
  50. P

    On conditional probability of an exponential random variable

    You are given a random exponential variable X: f(x) = λ exp(-λ x). Suppose that X = Y + Z, where Y is the integral part of X and Z is the fractional part of X: Y = IP(X), Z = FP(X). Which is the following conditional probability: P(Z < z | Y = n) for 0 ≤ z < 1 and n = 0, 1, … ?
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