Math Problem Statement

Evaluate the limits of the function ℓ(t) = 1 / (1 + e^(-t)) as t approaches 0, ∞, and -∞.

Solution

The second image shows the function (t)\ell(t) as:

(t)=11+et\ell(t) = \frac{1}{1 + e^{-t}}

We are tasked with evaluating the following limits for (t)\ell(t):

  1. limt0(t)\lim_{t \to 0} \ell(t)
  2. limt(t)\lim_{t \to \infty} \ell(t)
  3. limt(t)\lim_{t \to -\infty} \ell(t)

Solving the limits

  1. limt0(t)\lim_{t \to 0} \ell(t): Substitute t=0t = 0 into (t)\ell(t): (0)=11+e0=11+1=12\ell(0) = \frac{1}{1 + e^{0}} = \frac{1}{1 + 1} = \frac{1}{2} Answer: 12\frac{1}{2}

  2. limt(t)\lim_{t \to \infty} \ell(t): As tt \to \infty, et0e^{-t} \to 0, so: (t)=11+et11+0=1\ell(t) = \frac{1}{1 + e^{-t}} \to \frac{1}{1 + 0} = 1 Answer: 11

  3. limt(t)\lim_{t \to -\infty} \ell(t): As tt \to -\infty, ete^{-t} \to \infty, so: (t)=11+et11+=0\ell(t) = \frac{1}{1 + e^{-t}} \to \frac{1}{1 + \infty} = 0 Answer: 00

Let me know if you want any additional details or further clarification.


Here are some follow-up questions to extend this topic:

  1. What is the derivative of (t)\ell(t) with respect to tt?
  2. How does the function (t)\ell(t) behave for large positive and negative values of tt?
  3. Can you graph the function (t)\ell(t) and its asymptotes?
  4. What is the second derivative of (t)\ell(t), and what does it tell us about the concavity of the function?
  5. How would you interpret (t)\ell(t) in the context of logistic growth?

Tip: When evaluating limits involving exponentials, always consider how ete^t behaves as tt \to \infty and tt \to -\infty.

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Math Problem Analysis

Mathematical Concepts

Limits
Exponential Functions

Formulas

ℓ(t) = 1 / (1 + e^(-t))

Theorems

Limit properties of exponential functions

Suitable Grade Level

Grades 11-12 (Calculus)