ENGM1180 - Limits and Continuity

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Questions and Answers

What is the primary focus when using the 'method of exhaustion' to find the area of a shape?

  • Measuring the weight of the shape to estimate the area.
  • Dividing the shape into equal squares and counting them.
  • Calculating the precise dimensions using complex formulas.
  • Inscribing and circumscribing polygons to approximate the area. (correct)

The tangent line to a curve at a given point $P$ is best described as:

  • A line that is perpendicular to the curve at point $P$.
  • A line that touches the curve at $P$ and represents the limiting position of secant lines through $P$. (correct)
  • A line that intersects the curve at two distinct points close to $P$.
  • A line that is parallel to the x-axis and passes through point $P$.

What condition must be met for $\lim_{x \to a} f(x)$ to exist?

  • The one-sided limits, $\lim_{x \to a^-} f(x)$ and $\lim_{x \to a^+} f(x)$, must both exist and be equal. (correct)
  • The value of $f(a)$ must be equal to zero.
  • The function $f(x)$ must be defined at $x = a$.
  • The function $f(x)$ must be continuous at $x = a$.

Given $f(x) = \frac{x^2 - 4}{x - 2}$, how can the limit as $x$ approaches 2 be determined algebraically?

<p>By factoring the numerator and canceling common factors before evaluating the limit. (B)</p> Signup and view all the answers

If $\lim_{x \to a^-} g(x)$ and $\lim_{x \to a^+} g(x)$ both do not exist, what can be concluded about $\lim_{x \to a} g(x)$?

<p>The limit $\lim_{x \to a} g(x)$ does not exist. (A)</p> Signup and view all the answers

According to the definition of a limit, what does the statement $\lim_{x \to a} f(x) = L$ imply?

<p>As $x$ gets arbitrarily close to $a$, the values of $f(x)$ get arbitrarily close to $L$. (D)</p> Signup and view all the answers

What is the significance of evaluating one-sided limits?

<p>One-sided limits help to determine if the overall limit exists at a certain point. (C)</p> Signup and view all the answers

Given the function $H(t) = \begin{cases} 0 & \text{if } t < 0 \ 1 & \text{if } t \geq 0 \end{cases}$, what can be said about $\lim_{t \to 0} H(t)$?

<p>The limit does not exist. (C)</p> Signup and view all the answers

Which of the following is true regarding the fundamental limit laws?

<p>The limit of a sum is the sum of the limits, provided each of the individual limits exists. (A)</p> Signup and view all the answers

What must be true for a function $f$ to be continuous at a number $a$?

<p>$f(a)$ must be defined, $\lim_{x \to a} f(x)$ must exist, and $\lim_{x \to a} f(x) = f(a)$. (B)</p> Signup and view all the answers

When is a discontinuity considered 'removable'?

<p>When the limit exists at that point, but is not equal to the function's value or the function is not defined at that point. (A)</p> Signup and view all the answers

How is continuity defined over a closed interval $[a, b]$?

<p>The function must be continuous on the open interval $(a, b)$, and the limits as $x$ approaches $a$ from the right and $b$ from the left must exist and equal $f(a)$ and $f(b)$ respectively. (A)</p> Signup and view all the answers

What can be said about the continuity of a polynomial function?

<p>Polynomial functions are continuous everywhere. (D)</p> Signup and view all the answers

If function $g$ is continuous at $a$ and function $f$ is continuous at $g(a)$, what can be said about the composite function $f(g(x))$?

<p>The composite function $f(g(x))$ is continuous at $a$. (C)</p> Signup and view all the answers

Which statement best describes the Squeeze Theorem?

<p>If a function is squeezed between two other functions that approach the same limit, then the function must also approach that limit. (D)</p> Signup and view all the answers

What does it mean for $\lim_{x \to a} f(x) = \infty$?

<p>The function $f(x)$ increases without bound as $x$ gets closer to $a$. (D)</p> Signup and view all the answers

What is an 'indeterminate form' when evaluating limits?

<p>A form where the value of the limit cannot be determined directly and requires further analysis. (D)</p> Signup and view all the answers

What general strategy can be used to evaluate limits of rational functions at infinity when an indeterminate form is encountered?

<p>Divide the numerator and denominator by the highest power of $x$ in the denominator. (B)</p> Signup and view all the answers

Given that $f(x) = \frac{\sin(x)}{x}$, what is the limit as $x$ approaches 0?

<p>1 (C)</p> Signup and view all the answers

Which of the following functions is continuous at every point in its domain?

<p>$f(x) = \sqrt{x}$ (C)</p> Signup and view all the answers

A rational function $f(x) = \frac{P(x)}{Q(x)}$ is continuous everywhere except where?

<p>Where Q(x) = 0 (B)</p> Signup and view all the answers

To show that $\lim_{x \to 0} x^2 \sin(\frac{1}{x}) = 0$, what theorem is most applicable?

<p>The Squeeze Theorem (B)</p> Signup and view all the answers

What is implied by the statement $\lim_{h \to 0} \frac{f(x+h) - f(x)}{h}$?

<p>The instantaneous rate of change of $f$ with respect to $x$. (B)</p> Signup and view all the answers

In the context of limits, what does the term 'vertical asymptote' indicate?

<p>The function approaches infinity as $x$ approaches a specific value. (D)</p> Signup and view all the answers

How are one-sided limits related to vertical asymptotes?

<p>One-sided limits approaching different infinite values indicate a vertical asymptote. (A)</p> Signup and view all the answers

Assuming a polynomial function $p(x)$ of degree $n > 0$ and a real number $a_n > 0$, what is the $\lim_{x \to \infty} p(x)$?

<p>$\infty$ (B)</p> Signup and view all the answers

If a function has a removable discontinuity at $x=a$, what can be done to make the new function continuous?

<p>Redefine the function at $x=a$ to be equal to the limit as $x$ approaches $a$. (B)</p> Signup and view all the answers

The velocity of a skydiver is modeled by $v(t) = \sqrt{\frac{32}{k}} \frac{1-e^{-2t\sqrt{32k}}}{1+e^{-2t\sqrt{32k}}}$. What does $\lim_{t \to \infty} v(t)$ represent?

<p>The skydiver's terminal velocity. (B)</p> Signup and view all the answers

What type of function is $f(x) = x^{100} - 2x^{37} + 75$, and where is it continuous?

<p>Polynomial function; continuous everywhere. (B)</p> Signup and view all the answers

What is the defining characteristic of the 'greatest integer function', denoted as $[x]$?

<p>It gives the largest integer less than or equal to $x$. (C)</p> Signup and view all the answers

$f(x) = \begin{cases} cx^2 + 2x & \text{if } x < 2 \ x^3 - cx & \text{if } x \geq 2 \end{cases}$. What value of $c$ makes this function continuous?

<p>c = 1 (A)</p> Signup and view all the answers

Given the function $f(x)=\frac{x+1}{x-2};$,$;\lim_{x \to 2^+}f(x)$ equals

<p>$\infty$ (D)</p> Signup and view all the answers

Given the graphed function find $\lim_{x \to 5^-} g(x)$

<p>2 (C)</p> Signup and view all the answers

Given the graphed function what number is $\lim_{x \to 5} g(x)$ equal to?

<p>2 (A)</p> Signup and view all the answers

When an expression equals an Indeterminate form can use which of the following rule or therom?

<p>All of the above (D)</p> Signup and view all the answers

Flashcards

Area via Exhaustion Method

Calculus approach using inscribed polygons. Area of circle is limit of inscribed polygon areas.

Area Problem

The central problem in the branch of calculus.

Tangent Line

A line that touches a curve at a point.

Pierre Fermat

French mathematician (1601-1665); ideas behind differential calculus.

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Limit

Condition where function values get indefinitely close to a value as input approaches some point.

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Left-Hand Limit

The limit of f(x) as x approaches 'a' from the left.

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Right-Hand Limit

The limit of f(x) as x approaches 'a' from the right.

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One-Sided Limits

Limits evaluated from the left and right.

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Existence of a Limit

The limit exists if and only if both one-sided limits exist and are equal.

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Notion of Limit

Analyzing function behavior nearby, not exactly at, a point of interest.

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Definition of a Limit

lim f(x) = L if f(x) approaches L as x approaches a.

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Formal Definition of Limit

Suppose f(x) is defined when x is near the number a. We write lim x→a f(x) = L

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Limit Does Not Exist

If the left-hand limit does not equal the right-hand limit, the limit does not exist.

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Factor then find limit

Evaluate both sides for same value

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Continuous Function

A function f is continuous at a number a if lim x→a f(x) = f(a).

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Continuity Conditions

Function f is continuous at x = a if:

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Which functions are continous?

Types of functions that are continuos at every number in their domains.

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Infinite Limit

lim h(x) = ∞ means h(x) increases without bound as x gets close.

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Horizontal Asymptote

y = f(x) approaches the line y = b as x increases or decreases without bound.

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Highest Power of x in Denominator

Rule to solve indeterminate form by numerator times 1/x, and denominator times 1/x

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Study Notes

ENGM1180 – Mathematics for Engineers II: Lecture 1 – Limits & Continuity

  • Course Code: ENGM1280
  • Course Title: Mathematics for Engineers II
  • Ramone R. Jackson is the lecturer.
  • Office hours operate under an open door policy and are subject to availability.
  • Location: Room #4, Ground floor, Faculty of Engineering
  • Email: ramerjackson01@gmail.com
  • Class Times & Venue: Tuesdays – Thursdays 8:00am - 9:00am SLT 2
  • Assessments:
  • Assignments: 20%
  • Project: 20%
  • In-Course: 20%
  • Final exam: 40%

Formulas and Theorems

  • The slides include various algebraic, arithmetic, and geometric formulas.
  • It also include factoring, binomial theorem, trigonometric identities and functions.

Area Problem

  • Ancient Greeks used the "method of exhaustion" to find areas around 2500 years ago.
  • They could find the area A of any polygon by dividing it into triangles.
  • The Greek method of exhaustion was to inscribe polygons in a figure and circumscribe polygons around the figure.
  • They would then increase the number of sides of the polygons.
  • Eudoxus (fifth century BC) used exhaustion to prove the formula for the area of a circle: A = πr².
  • The area problem is the central problem in integral calculus.

Tangent Problem

  • Differential calculus came about due to the tangent problem.
  • It was not invented until 2000 years after integral calculus.
  • Key figures: Pierre Fermat (1601-1665), John Wallis (1616-1703), Isaac Barrow (1630-1677), Isaac Newton (1642-1727), and Gottfried Leibniz (1646-1716).

Limits

  • Functions can be undefined at certain points like x = 2.
  • Tables and graphs can give clues about a function's behavior.

One-Sided Limits

  • Notation x → 2⁻ indicates x approaches 2 from the left side.
  • Notation x → 2⁺ indicates x approaches 2 from the right side.
  • lim x→2⁻ f(x) and lim x→2⁺ f(x) are one-sided limits.
  • If the two one-sided limits of f(x) are the same as x approaches a, then the limit of f(x) as x approaches a exists.

Limit Definition

  • If f(x) is defined when x is near a number a, then lim x→a f(x) = L if f(x) can be made arbitrarily close to L by taking x sufficiently close to a, but not equal to a.
  • lim x→a f(x) = L if and only if lim x→a⁻ f(x) = L and lim x→a⁺ f(x) = L.

Limit Laws

  • Suppose that c is a constant and the limits lim x→a f(x) and lim x→a g(x) exist. Then:
  • lim x→a [f(x) + g(x)] = lim x→a f(x) + lim x→a g(x)
  • lim x→a [f(x) - g(x)] = lim x→a f(x) - lim x→a g(x)
  • lim x→a [cf(x)] = c lim x→a f(x)
  • lim x→a [f(x)g(x)] = lim x→a f(x) ⋅ lim x→a g(x)
  • lim x→a [f(x) / g(x)] = lim x→a f(x) / lim x→a g(x) if lim x→a g(x) ≠ 0
  • lim x→a [f(x)]ⁿ = [lim x→a f(x)]ⁿ where n is a positive integer.
  • lim x→a c = c
  • lim x→a x = a
  • lim x→a xⁿ = aⁿ where n is a positive integer.
  • lim x→a ⁿ√x = ⁿ√a where n is a positive integer. (If n is even, we assume that a > 0.)
  • lim x→a ⁿ√f(x) = ⁿ√lim x→a f(x) where n is a positive integer. (If n is even, we assume that lim x→a f(x) > 0.)
  • If f is a polynomial or a rational function and a is in the domain of f, then lim x→a f(x) = f(a)

Theorems

  • If lim x→a f(x) = L and lim x→a g(x) = L, then lim x→a f(x) = L
  • Suppose that f(x) ≤ g(x) ≤ h(x) for all x in some interval (c, d), except possibly at the point a ∈ (c, d) and that lim x→a f(x) = lim x→a h(x) = L. Then, it follows that lim x→a g(x) = L.
  • Any polynomial is continuous everywhere on R = (-∞, ∞).
  • Any rational function is continuous wherever it is defined; that is, it is continuous on its domain.
  • If f is continuous at b and lim x→a g(x) = b, then lim x→a f(g(x)) = f(b).
  • If g is continuous at a and f is continuous at g(a), then the composite function f ∘ g given by (f ∘ g)(x) = f(g(x)) is continuous at a.

Function Types

  • The following types of functions are continuous at every number in their domains
  • polynomials
  • rational functions
  • root functions
  • trigonometric functions

Definition of Continuity

  • A function f is continuous at a number a if lim x→a f(x) = f(a).
  • The definition implicitly requires: f(a) is defined, lim x→a f(x) exists, and lim x→a f(x) = f(a).
  • If a function f is continuous at every point on an open interval (a, b), then it is continuous on (a, b).
  • If it is continuous on the open interval (a, b) and lim x→a+ f(x) = f(a) and lim x→b- f(x) = f(b), then the function f is continuous on the closed interval [a, b].
  • A function f is continuous on an interval if it is continuous at every number in the interval.
  • If f is defined only on one side of an endpoint of the interval, continuous at the endpoint is understood to mean continuous from the right or continuous from the left.

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