
Please post any and all homework or other textbookstyle problems in one of the Homework & Coursework Questions...

Feb2313 09:24 AM
micromass

1 
45,340 
Let f(x,y) = ( \frac{y}{x^2 + y^2}, \frac{x}{x^2 + y^2}) with f : D \subset \mathbb{R}^2 \to \mathbb{R}^2
I...

Dec2411 07:13 AM
Damidami

3 
1,224 
What does this mean ! ?

Jul1708 10:41 PM
mathwonk

2 
1,551 
jjjj

Jan3108 09:44 AM
HallsofIvy

1 
3,825 
Consider the heat equation in a radially symmetric sphere of radius unity:
u_t = u_{rr}+{2 \over r}u_r \ for \ (r,t)...

Aug2709 02:44 PM
tinytim

1 
638 
Use the chain rule to show that
dz/dx = (cos(theta) * dz/dr)  (1/r * sin(theta) dz/dtheta) and
dz/dy =...

Sep813 03:59 AM
CompuChip

1 
601 
I define a consistent family, F, to be a set of intervals such that if I_1 and I_2 are in F then I_1 and I_2...

Feb2808 08:11 PM
Pere Callahan

6 
1,727 
Is there a formula that will calculate time when I know the following...?
Initial velocity = 0 Final velocity =...

Sep1108 07:59 AM
Photon713

3 
1,676 
If we parameterize the arc length of a vector valued
function, say, r(s) and r(s) has constant curvature
(not equal...

Mar2110 11:29 PM
Tinyboss

1 
1,098 
Find a number "k" such that exist only one intersection between the curve exponential k^x e and the straight x·k. This...

Nov1713 05:54 PM
PSarkar

5 
540 
My book (Saff&Snider) has the following theorem
Suppose u(x,y) is a realvalued function defined in a domain D. If...

Jun1409 09:33 PM
Tibarn

4 
1,034 
This is a question that came up in a conversation with my father who was a fighter pilot in ww2... we got to talking...

Mar610 01:20 PM
CompuChip

2 
3,126 
Hi everyone,
I've been racking my brain about this problem, but can't seem to figure it out. It seems like it...

Jun1113 07:49 PM
WannabeNewton

3 
772 
The first order KKT condition for constrained optimization requires that the gradient for the Lagrangian is equal to...

Apr1212 02:56 PM
brydustin

4 
981 
Hi,
I want to know the solution of the following equation.
a = argmin_{a} \\
where x_i, y_i are column vectors...

Apr1511 05:29 AM
jasonRF

2 
2,767 
Hi,
I need help with this problem;
minimize x^3, subject to K= xΩπ
so would the solution be
KΩπ=x

Apr1412 07:58 AM
HallsofIvy

1 
988 
I'm trying to find the regular parallelepiped with sides parallel to the coordinate axis inscribed in the ellipsoid...

Jul208 09:38 AM
HallsofIvy

1 
1,213 
I have the analytical first and second derivatives of a (multidimensional) lagrangian ( l = f  λh). X is the vector...

Jan2112 05:04 PM
brydustin

0 
947 
Construct a compact set of real numbers whose limit points form a
countable set.

Oct804 09:35 AM
forget_f1

8 
4,447 
Suppose I'd like to construct a C^\infty generalization of a characteristic function, f(x): \mathbb R \to \mathbb R,...

Oct3111 02:32 PM
Citan Uzuki

1 
1,386 
Today, I had the desire to construct a C^{\infty} approximation to a tent function. Specifically, for any positive...

Mar1306 11:39 PM
Hurkyl

5 
1,654 
How do you construct Peano curves? All pictures I have seen suggest that it is iterative process, however, I don't...

Sep2208 05:50 PM
Borek

0 
799 
Hello
I am reading a paper on numerical methods which requires a 2D function to be converted to a 1D function. ...

Mar210 09:43 AM
nkinar

2 
868 
Can you prove that \mathbf{R} and \mathbf{R}\mathbf{Q} have same cardinality?
One way would be to say that...

Sep1908 06:25 AM
morphism

3 
1,798 
This proof I think is related to our construction of R in class using equivalences classes of Cauchy sequences:
Let...

Nov311 04:01 PM
autre

3 
1,080 
I was looking at the construction of the real number system.
I know dedekind cuts can be used(completely worthless...

Mar2511 01:38 PM
Liangpan

16 
2,807 
Hi!!I am trying to construct in Matlab a Cinfinity Odd Finction whose time derivative is always positive. The...

Oct2306 08:22 PM
StatusX

3 
2,902 
I have a question regarding this.
I wish I were home right now so I can give the exact words.
Anyways, the book...

Feb1606 12:02 PM
HallsofIvy

7 
1,830 
Let be a differential equation :
y^{(n)}=F(t,y,\dot y ,\ddot y , \dddot y,..........., y^{n1})
then if we...

Jun1006 05:54 AM
eljose

0 
1,051 
suppose i have a real function f=f(x)
this function is smooth everywhere on the real line
for example, f=e^x.
...

Mar1910 08:22 AM
dalle

5 
858 
for any function f(x) how can you convert it to continued fractions in the form:
...

May1807 08:58 AM
NateTG

1 
913 
Does the continued product of fractions 1/2 x 2/3 x 3/4 x.....x (n1)/n converge? If so, what does it converge to?

Apr509 08:58 PM
SW VandeCarr

4 
1,293 
I'm seeking a bit of affirmation or correction here before i try to solidify this to memory....
I know continuity...

Nov1604 03:54 PM
NateTG

6 
10,599 
How come sin(x^1) is not continuous and xsin(x^1) is?

Nov1610 09:01 AM
HallsofIvy

12 
6,093 
X, Y metric spaces. f:X>Y and X is compact.
How do I prove that f is continuous if and only if G(f)={(x,f(x)):x in...

Oct2908 07:30 PM
mathwonk

9 
1,799 
Consider f(x)=x^3x^2+x+1
g(x)=\left\{\begin{array}{cc}{max\{f(t),0\leq t \leq x\}}\;\ 0\leq x \leq 1
\\ 3x\;\...

Jan1004 04:14 PM
Moni

1 
1,975 
My question is best stated by using an example:
Suppose f is a function defined only for rational x, and for...

Sep3009 09:37 AM
lurflurf

2 
901 
Can anyone help me with this problem?
Say f(x) & g(x) are cont. at x=5.
Also that f(5)=g(5)=8.
If h(x)=f(x)...

Aug308 11:17 AM
peos69

7 
1,468 
I'm just wondering why in the definition of continuity, limit of function, or even just limit of a sequence, the...

Feb1610 04:39 PM
Bleys

2 
1,101 
Hello, I've allways wondered how to get to polar coordinates from cartisan coordinates. I took a course in fluid...

Feb2113 04:35 PM
pasmith

1 
553 
Just curious how to define continuity for mult dim. functions. I know that the topological and set theorectical...

Dec1910 08:42 AM
brydustin

5 
3,640 