Homework Statement
Homework Equations
Ability to graph functions.
Essential Discontinuity:
Jump discontinuity or Infinite discontinuity
The Attempt at a Solution
First Question:
After plugging in 2 for every equation and getting a result that was greater than 0, I...
Homework Statement
Let
\begin{equation*}
f(x,y) = \begin{cases} \dfrac{x^3 - y^3}{x^2 + y^2}, \hspace{1.1em} (x, y) \neq (0,0) \\ 0, \hspace{4em} (x,y) = (0,0) \end{cases}
\end{equation*}
Is f continuous at the point (0,0)? Are f_x og f_y continuous at the point (0,0)?
Homework Equations...
Homework Statement
A large vertical cylindrical rainwater collection tank of cross sectional area A is filled to a
depth h. The top of the tank is open and in the centre of the bottom of the tank is a small hole
of cross sectional area B (B<<A). Derive expressions for (i) the flow speed...
my book says, the function y = x*sin(1/x) is not continuous at x = 0, however by defining a new function by
F(x) =
x*sin(1/x) , x ≠ 0
0 , x = 0
then F is continuous at x = 0.
This does not make sense to me because the limit as x → 0 is equal to 1, not zero...
Why does the book say if f(x) is continuous at a then
lim ( f(a + Δx) - f(a) ) / Δx, that Δx will go to zero. What does that mean geometrically?
Δx→0
More importantly, why would Δx not approach zero if f(x) is not continuous at a?
Im guessing it has something to do with the slopes of...
Since I am new to PF (hi!), before I go any further, I would like to
a) briefly note that this is an independent study question, and that its scope goes beyond that of a textbook question - i.e., I believe that this thread belongs here - and
b) also note that I am new to analysis and early...
Was trying to learn differential geometry, had to take time off of it to develop some knowledge of topology, namely compactness and Hausdorff's condition. I'm using Sutherland's book on topology and came across something I didn't understand concerning metric spaces,
Sutherland speaks of the so...
A function f is defined as follows:
f(x) = 2cos(x) if x≤c,
= ax^2 + b if x > c .
Where a,b, and c are constants. If b and c are given. find all values of a for which f is continuous at the point x = c
Solution:
a = (2cos(c) - b)/c^2 if c ≠ 0 ; if c = 0 there is...
Homework Statement
This isn't really a problem but it is just something I am curious about, I found a theorem stating that you have two metric spaces and f:X --> Y is uniform continuous and (xn) is a cauchy sequence in X then f(xn) is a cauchy sequence in Y.
Homework Equations
This...
Hi, I have a project where I have to speak about some applications of the mass continuity equation for fluids. I only found this http://www.efm.leeds.ac.uk/CIVE/CIVE1400/Section3/continuity.htm, but that's not enough. What else do you think I can speak about?
Explain why this is no good as a definition of continuity at a point a (either by giving an example of a continuous function that does not satisfy the definition or a discontinuous one that does):
Given ε > 0 there exists a \delta > 0 such that |x – a| < \epsilon \Rightarrow |f(x) – f(a)| <...
I'm having a little trouble with something so I am wondering,
If f is a continuous 1-1 mapping from an open set (a,b) into ℝ then is its inverse function g continuous at all points of the image of f?
My argument is that g(y) is in (a,b) for all y in the image of f, and g(y)=x for some x in...
Let I be an open interval and f : I → ℝ is a function. How do you define "f is continuous on I" ?
would the following be sufficient? :
f is continuous on the open interval I=(a,b) if \stackrel{lim}{x\rightarrow}c \frac{f(x)-f(c)}{x-c} exists \forall c\in (a, b)
is this correct?
Also, what...
Hi!
I'm trying to implement an implicit scheme for the continuity equation.
The scheme is the following:
http://img28.imageshack.us/img28/3196/screenshot20111130at003.png
With \rho being the density, \alpha is a weighing constant. d is a parameter that relates the grid spacing to the...
If f is continuous function and (x_n) is a sequence then x_n \to x \implies f(x_n) \to f(x)
The converse f(x_n) \to f(x) \implies x_n \to x in general isn't true but why is it true, for example, if f is arctan?
I am self-studying Calculus and tried to solve the following question:
Homework Statement
Suppose that the function f is continuous and increasing in the closed interval [a, b]. Then
(i) f has an inverse f-1, which is defined in [f(a), f(b)];
(ii) f-1 is increasing in [f(a), f(b)];
(iii) f-1...
If a function f is continuous at a point p, must there be some closed interval [a,b] including p such that f is integrable on the [a,b]?
As a definition of integrable I'm using the one provided by Spivak: f is integrable on [a,b] if and only if for every e>0 there is a partition P of [a,b]...
Homework Statement
Water flows through a horizontal tapered pipe. At the wide end its speed is 4.0 m/s and at the narrow end it is 5.0 m/s. The pressure in the wide pipe is 2.5 x 10^5 Pa. What is the pressure in the narrow pipe?
a. 2.5 x 10^2 Pa
b. 3.4 x 10^3 Pa
c. 4.5 x 10^3 Pa
d. 2.3 x...
Homework Statement
If f(x) = 3 for x < 0 and f(x) = 2x for x ≥ 0, is f(x) differentiable at x = 0? State and justify why/why not.
Homework Equations
The Attempt at a Solution
Obviously, since f(x) is not continuous and the limit doesn't exist as x\rightarrow0, the function...
You know that fx(x0,y0) exists. What can you tell about the continuity of g(x)=f(x, y0) at x=x0?
I know the answer is that it is continuous but I just wanted somebody to confirm why.
I'm working on a problem for my analysis class. Here it is:
Let f be differentiable on an open subset S of R. Suppose there exists M > 0 such that for all x in S, |f'(x)| ≤ M, i.e. the derivative is bounded. Show that f is uniformly continuous on S.
I'm not too sure that this question is...
Hi,
can anyone help me ?
Given Topological Spaces (metric spaces) (X, d1) and (Y,d2), show that a function f: X -> Y is continuous if and only if f(cl of A) is a subset of cl of f(A) for all A subset X1.
How can i proof this ?
Thank you!
The first hypothesis is that f is continuous on [a,b]...
Is there a more concise mathematical way of saying... "because the function f is a polynomial it is continuous in its domain."? Because I rather not write that on my test it looks sloppy and non professional...
Why some functions that are continuous on each closed interval of real line fails to be uniformly continuous on real line. For example x2. Give conceptual reasons.
From the viewpoint of the continuity principle, we know that the stream of water is fatter near the mouth of the faucet and skinner lower down.
The question is how single molecules understand when/how they should deviate from their perpendicular free fall to a deviated one ?
Homework Statement
Using the definition of continuity, prove that the function f(x) = sin x
is continuous.
Hint: sin a − sin b = 2 sin (a-b)/2 . cos (a+b)/2Homework EquationsThe Attempt at a Solution
Using the idea that:
|sin(x)| ≤ |x|
|cos(x)| ≤ 1
along with the hint: sin a − sin b = 2...
Homework Statement
Prove that a continuous linear functional, f is bounded and vice versa.
Homework Equations
I know that the definition of a linear functional is:
f( \alpha|x> + \beta|y>) = \alpha f(|x> ) + \beta f( |y> )
and that a bounded linear functional satisfies:
||f(|x>)) ||...
Homework Statement
Show that f(x) = \sum_{i=1}^{\infty}\frac{2^{i}x - \lfloor 2^{i}x \rfloor}{2^{i}} is continuous at all real numbers, excluding integers.
The Attempt at a Solution
I've tried going about via |f(x) - f(y)| < ε, but am having trouble with this, since first, I don't get anywhere...
Ok, so basically I am trying to decide whether my mathematics is valid or if there is some subtly which I am missing:
Lets say I have a 1-1 strictly increasing point-wise continuous function f: R -> R, and I want to show that the inverse function g: f(R) -> R is also point-wise continuous...
Homework Statement
If the domain of a continuous function is an interval, show that the image is an interval.
Homework Equations
Theorem from book: f is a cont. function with compact domain D, then f is bounded and there exists points y and z such that f(y) = sup{ f(x) | x ∈ D} and...
HELP! real analysis question: continuity and compactness
Homework Statement
Let (X,d) be a metric space, fix p ∈ X and define f : X → R by f (x) = d(p, x). Prove that f is continuous. Use this fact to give another proof of Proposition 1.126.
Proposition 1.126. Let (X, d) be a metric space...
This isn't so much of a homework problem as a general question that will help me with my homework.
I am supposed to prove that a given function is uniformly continuous on an open interval (a,b).
Since for any continuous function on a closed interval is uniformly continuous, I am curious...
I know its a pretty elementary question, but I never felt like I've had any sort of reasonable explanation of why. As I understand, we can define continuity for a function f: ℝn→ℝ as:
For any ε>0 there exists a δ>0 such that for all x st 0< lx - al < δ then lf(x) - f(a)l < ε
Alright, so...
Homework Statement
Let X and Y be metric spaces, f a function from X to Y:
a) If X is a union of open sets Ui on each of which f is continuous prove that f is continuous on X.
b) If X is a finite union of closed sets F1, F2, ... , Fn on each of which f is continuous, prove that f is continuous...
Homework Statement
I have an upcoming math test, and these are from the sample exam. I'll post my solutions as I go along. I've submitted this post as is and am going to edit in my attempts. A few of these are "verify my proof is rigorous" others are "i've no idea what I'm doing
1 Using simple...
Homework Statement
Given each of the functions f below, describe the set of points at which the Fourier
series converges to f.
b) f(x) = abs(sqrt(x)) for x on [-pi, pi] with f(x+2pi)=f(x)
Homework Equations
Theorem: If f(x) is absolutely integrable, then its Fourier series converges to f...
Homework Statement
f:R->R is defined as f(x) when x\neq 0, and 1 when x=0.
Find f'(0).
Homework Equations
The Attempt at a Solution
Since I can prove that f is continuous at x=0, does that allow me to take the the limit of f'(x) as x-> 0, which is 0? It is quite easy to...
Homework Statement
f(x) = x^3 [cos(pi/x^2) + sin(pi/x^2)] for x≠0
Homework Equations
The Attempt at a Solution
I really am stuck.
I've tried squeeze theorem on [cos(pi/x^2) + sin(pi/x^2)], but I can't compute the range.
So, I tried doing it individually, squeezing -1 ≤...
Homework Statement
Find a value for k to make f(x) continuous at 5
f(x)= sqrt(x2-16)-3/(x-5) if x cannot equal 5
3x+k when x=5
Homework Equations
none
The Attempt at a Solution
lim x->5 sqrt((x+4)(x-4))-3/(x-5) * sqrt((x+4)(x-4))+3/sqrt((x+4)(x-4))+3
lim x->5...
I have 2 questions in regards to continuity and limits.
Question 1:
f(x)= e^{-x^{2}} if x ≠ 0.
f(x)= c if x=0.
For which value of c is f(x) continuous at x=0?
I was thinking the answer would be 1 but I feel that's incorrect.
Question 2:
Compute lim x→∞f(x).
I'm not familiar with how to...
Homework Statement
2 problems.
1)
Find an example of a function f such that :
the line y=2 is a horizontal asymptote of the curve y=f(x)
the curve intersects the line y=2 at the infinitive number of points
2)
The position of an object moving along x-axis is given at time t by:
s(t)= 4t-4 if...
I have a function in x and y, and I was trying to figure out if it was continuous or not.
f(x,y)=\frac{x^2-y^2}{(x^2+y^2)^2}
As far as I know, the only problematic point in the domain is (x,y)=(0,0) so I tried to use the \epsilon,\delta definition.
My proposed limit at (0,0) being 0...
Hey guys,
Continuity is generally expressed as lim x->a f(x)=f(a).
But is it also correct to express it as: lim h->0 f(x+h) - f(x) = 0?
Because that would imply that all numbers around f(x) would have to be very close to f(x), and that is basically what continuity is, no?
Homework Statement
Prove that f(x) = x^2 is continuous at x = 2 using the ε - ∂ definition of continuity.
2. The attempt at a solution
Using the definition of continuity, I've reached thus far in the question:
|x - 2||x + 2| < ε whenever |x - 2| < ∂
3. Relevant equations
I...
Hello
I have found in some textbooks that the magnetic scalar potential is continuous across a boundary. Now, how can this be explained starting from the two boundary conditions of Maxwell's equations (continuity of normal flux density Bn and tangential field Ht)?
Thanks in advance for...
Homework Statement
Define
f = { x^2 if x \geq 0
x if x < 0
At what points is the function f | \Re -> \Re continous? Justify your answer.
Homework Equations
A function f from D to R is continuous at x0 in D provided that whenever {xn} is a sequence in D that converges to x0, the...
Example 8 in photo 1 shows that differentiability doesn't implies continuity.
But photo 2 shows a Theorem that contradict to photo 1.
I wonder what is going on here.
Does the textbook get it wrong?
Homework Statement
a) Determine the points where the function f (x) = (x + 3) / (x^2 − 3x − 10) is discontinuous. Then define a new function g that is a a continuous extension of f .
b) Determine what value of the constant k makes the Piecewise function
{ (x − k)/ (k^2 + 1) ...