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HallsofIvy
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Yesterday,
11:54
MarkFL
replied to a thread
Differentiation challenge
in
Challenge Questions and Puzzles
We appreciate challenge problems of virtually any level of difficulty. My advice to everyone is that if you find a posted problem "too easy" to...
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5 replies | 106 view(s)
January 19th, 2017,
20:26
HallsofIvy
replied to a thread
Differentiation challenge
in
Challenge Questions and Puzzles
How is this a "challenge"? Once you have multiplied on both sides by y(x+ y), it is a straight forward Calculus I "implicit differentiation".
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5 replies | 106 view(s)
January 19th, 2017,
10:19
MarkFL
replied to a thread
Minimum of function under constraint
in
Calculus
Yes, the function as a whole is not bounded from below or from above. Let's look at this using Lagrange Multipliers... We have the objective...
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6 replies | 72 view(s)
January 19th, 2017,
08:50
HallsofIvy
replied to a thread
Extrema of function - What is λ?
in
Calculus
I wondered where "\lambda" came from! There is no "\lambda" in the statement of the problem so if the problem asks you to find it then, yes, it is...
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2 replies | 43 view(s)
January 19th, 2017,
08:44
HallsofIvy
replied to a thread
Derivative of function
in
Analysis
I suspect that they are referring to your step "\lim_{x\to 0^+} x^{a- 1}e^{-\frac{1}{x^2}}= 0 for all a". That is true but how you prove it is true...
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2 replies | 53 view(s)
January 18th, 2017,
22:47
MarkFL
replied to a thread
Minimum of function under constraint
in
Calculus
You also need to check the boundaries of the function, one of which is $x=0$, at which the function is discontinuous. Another way to find the range...
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6 replies | 72 view(s)
January 18th, 2017,
20:13
MarkFL
replied to a thread
Minimum of function under constraint
in
Calculus
The function: f(x)=\frac{36}{x}+x has 2 local extrema, but we need to also look at the range, which is $(-\infty,-6]\,\cup\,[6,\infty)$. You...
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6 replies | 72 view(s)
January 17th, 2017,
17:35
MarkFL
replied to a thread [SOLVED]
231.12.3.63 Determine the smallest distance between point P and the line L through the origin
in
Calculus
The square of the distance is: D^2=(x+8)^2+(6x-4)^2=37x^2-32x+80 Critical value is from: 74x-32=0\implies x=\frac{16}{37} ...
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2 replies | 60 view(s)
January 17th, 2017,
09:23
HallsofIvy
replied to a thread [SOLVED]
231.12.3.19 angle between vectors
in
Calculus
It is best to use the same notation as the problem. I would have written $\frac{(-7i- j)\cdot (-i- 7j)}{\sqrt{50}\sqrt{50}}$
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3 replies | 66 view(s)
January 16th, 2017,
17:17
MarkFL
replied to a thread
Parabola question
in
Pre-Algebra and Algebra
Yes, that's what I got too. (Yes) So then, what is $y_{\min}$?
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5 replies | 95 view(s)
January 16th, 2017,
16:04
MarkFL
replied to a thread
Parabola question
in
Pre-Algebra and Algebra
We know the axis of symmetry for the general quadratic: f(x)=ax^2+bx+c is the line: x=-\frac{b}{2a} And so for the given function:
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5 replies | 95 view(s)
January 15th, 2017,
15:03
MarkFL
started a thread
Smilie Tabs: Easier Access To Smilies
in
Announcements
Hello MHB Community! (Wave) We have just installed a new feature that will make adding smilies to your posts easier and more efficient. When you...
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3 replies | 109 view(s)
January 15th, 2017,
10:59
MarkFL
replied to a thread
Prove that sin(x)+cos(x) is equal or larger than 1
in
Trigonometry
We could use Lagrange Multipliers...consider the objective function: f(x,y)=\sin(x)-\sin(y) Subject to the constraint: ...
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11 replies | 281 view(s)
January 13th, 2017,
16:55
HallsofIvy
replied to a thread
Linear mapping
in
Linear and Abstract Algebra
"i" is not the index here, k is.
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10 replies | 209 view(s)
January 12th, 2017,
23:20
MarkFL
replied to a thread
Site upgrade and planned downtime Wed, Jan 11
in
Announcements
Yes, when I got in tonight, I found Jameson had sent me the cure for the thanks issue. (Dance)
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12 replies | 296 view(s)
January 12th, 2017,
22:41
MarkFL
replied to a thread
Site upgrade and planned downtime Wed, Jan 11
in
Announcements
After an upgrade to the latest version of our thanks product, that is now functioning again. (Yes)
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12 replies | 296 view(s)
January 12th, 2017,
16:33
MarkFL
replied to a thread
cone
in
Calculus
The vessel into which the water is flowing has a radius that is one half the height. Any "cone of water" partially or completely filling the vessel...
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3 replies | 82 view(s)
January 12th, 2017,
16:11
MarkFL
replied to a thread
cone
in
Calculus
At any point in time, how are the radius and height of the "cone of water" within the conical vessel related?
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3 replies | 82 view(s)
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Showing Friends 1 to 10 of 10
January 20th, 2017
16:56 -
topsquark
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Re: Differentiation challenge
by
HallsofIvy
How is this a...
January 19th, 2017
11:35 -
topsquark
clicked Thanks for this post:
Re: Derivative of function
by
HallsofIvy
I suspect that they are...
09:15 -
mathmari
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Re: Derivative of function
by
HallsofIvy
I suspect that they are...
January 17th, 2017
10:35 -
karush
clicked Thanks for this post:
Re: 231.12.3.19 angle between vectors
by
HallsofIvy
It is best to use the...
January 13th, 2017
19:35 -
mathmari
clicked Thanks for this post:
Re: Linear mapping
by
HallsofIvy
Ah ok. So, is the...
January 6th, 2017
20:55 -
Joppy
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Re: Rigorous definition of "Differential"
by
HallsofIvy
Your restriction, that...
09:52 -
Fantini
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Re: Rigorous definition of "Differential"
by
HallsofIvy
Your restriction, that...
January 4th, 2017
14:55 -
HallsofIvy
clicked Thanks for this post:
Re: Resolution of polynomial
by
MarkFL
You could write: ...
03:11 -
karush
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Re: s4.13.5.41 relation of 2 planes
by
HallsofIvy
The problem asks you to...
January 3rd, 2017
14:12 -
MarkFL
clicked Thanks for this post:
Re: s4.13.5.41 relation of 2 planes
by
HallsofIvy
The problem asks you to...
14:03 -
MarkFL
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Re: determine mass
by
HallsofIvy
consider a torus whose...
January 1st, 2017
13:25 -
HallsofIvy
clicked Thanks for this post:
Re: Power series solution for Log(1+x)
by
Saknussemm
Taking the derivative of...
December 30th, 2016
09:42 -
HallsofIvy
clicked Thanks for this post:
Re: local max
by
MarkFL
Well, for part i) this...
December 29th, 2016
09:26 -
HallsofIvy
clicked Thanks for this post:
205.o8.14} what is the velocity when t=3
by
karush
$\tiny{205.o8.14}$...
09:14 -
HallsofIvy
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Re: Random Variable
by
vkalyan
[QUOTE=Jason123;90548]Und...
December 28th, 2016
19:20 -
HallsofIvy
clicked Thanks for this post:
Re: s6.803.12.5.9 are lines parallel?
by
MarkFL
A vector parallel to the...
03:07 -
karush
clicked Thanks for this post:
Re: s6.793.12.4.27area of a parallelogram
by
HallsofIvy
$\tiny{s6.12.4.27}$ The...