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Groups > sci.physics > #571275
| From | vallor <vallor@cultnix.org> |
|---|---|
| Newsgroups | alt.free.newsservers, alt.usenet.kooks, sci.physics |
| Subject | Re: Walking through a problem that uses a derivative |
| Date | 2016-04-18 06:24 +0000 |
| Message-ID | <dnjcslFroq2U1@mid.individual.net> (permalink) |
| References | (3 earlier) <dnf1lrFddd5U22@mid.individual.net> <2016c0381b63613e1e8c616ea2224e2a@dizum.com> <op.yf1uiaa1tm21m2@benson.localhost> <dni1p4FhphdU1@mid.individual.net> <ddc319104f5c725c43e8418da46c3c4e@dizum.com> |
Cross-posted to 3 groups.
On Mon, 18 Apr 2016 07:29:49 +0200, Friendly Neighborhood Vote Wrangler
Emeritus wrote:
> Time to spin the kooks up again. Melt, kooks, melt. <snicker>
>
> vallor (aka Scott Doty), in <news:dni1p4FhphdU1@mid.individual.net> did
> thusly jump head first into the wood chipper again:
>
>> On Sun, 17 Apr 2016 01:50:24 -0400, Robert Michael Wolfe the Pittsburgh
>> Pied Piper Of Penis (aka DildoRider) of 5907 Stanton Ave., Pittsburgh,
>> PA (aka Teh Mop Jockey),
>> socked up as sucksroot@127.0.0.1 wrote:
>
>>> On Sun, 17 Apr 2016 01:35:06 -0400, Friendly Neighborhood Vote
>>> Wrangler Emeritus <FNVWe@altusenetkooks.xxx> wrote:
>
>>>> vallor (aka Scott Doty), in <news:dnf1lrFddd5U22@mid.individual.net>
>>>> did thusly jump head first into the wood chipper again:
>
>>>>> On Sat, 16 Apr 2016 07:38:38 +0200, Friendly Neighborhood Vote
>>>>> Wrangler Emeritus wrote:
>
>>>>>>> I'm glad you caught that, I totally missed it. (Got just a couple
>>>>>>> of paragraphs into his post, then ennui set in.)
>
>>>>>> You caught Shiny Tinfoil Spankard wondering why x^2 and 2x aren't
>>>>>> co-functions?
>
>>>>> He never did that.
>
>>>> Sure he did.
>>>>
>>>> "The derivative of x^2 is 2x. Does that make them also co-functions?"
>
>>>>>> That's because he's a confused little kooktard.
>
>>>>> Looks more like you are _very_ confused.
>
>>>> Not really, you're just shifting the goal-posts and being ambiguous
>>>> in your diversionary bleating. LOL
>
>>>>>>> Let's see if we can generate a koan-like moment for the budding
>>>>>>> mathematician:
>>>>>>>
>>>>>>> d/dx( 2x^3 + 69 ) = 6x^2
>>>>>> d/dx(2x^3 + 69) = (3*(2x)^2 + 0) = 6x^2 = 2*6x = 12x
>
>>>> Correct. LOL
>
>>>>>> Did you forget to simplify? LOL
>
>>>>> That isn't "simplifying" you did, you took the second derivative.
>>>>>
>>>>> No where in my post did I try to muddy the waters with second
>>>>> derivatives, I was talking about the basics. Obviously.
>
>>>> You didn't specify what your goal was.
>
>>>>> So you get an "A" for effort, but I'm going to have to mark you down
>>>>> for being over-enthusiastic with the process.
>
>>>> Awww, he thinks he's a teacher... and he can't even read a graph. LOL
>
>>>>>>> d/dx( 4x^2 ) = 8x
>>>>>> d/dx(4x^2) = 2*(4x) = 8x
>
>>>> Correct.
>
>>>>>>> d/dx( 4x^2 + 7x + 3 ) = 8x + 7
>>>>>> d/dx(4x^2 + 7x +3) = (2*(4x) + 7 + 0) = 8x + 7
>
>>>> Correct.
>
>>>>>> You should try teaching Shiny Tinfoil Spankard. LOL
>
>>>>> I'll let you in on an open secret:
>>>>>
>>>>> He knows more about this than you do.
>
>>>> Really? Is that why he denied that a sinusoid is a transform of a
>>>> circle; denied that wave interference and superposition are the same
>>>> thing; denied that sin^2 is a sinusoid; claimed that "within 10%
>>>> error"
>>>> equaled "10% error"; didn't know what LaTeX notation was or that
>>>> there's a formula in that plain text LaTeX notation (he thought it
>>>> was a script. LOL!); didn't know what the "co" in cosine means nor
>>>> what co-functionality was nor the difference between inverse
>>>> operations and cofunctionality; didn't know that finding the
>>>> anti-derivative is the same as finding the integral; denied that
>>>> stock trading requires mathematical derivatives; claimed that
>>>> mathematical derivatives as used in stock trading are stock options;
>>>> demonstrated that he didn't know what the Fundamental Theorem of
>>>> Calculus is; demonstrated that he didn't know that the derivative of
>>>> a constant is always equal to zero; claimed that no math was being
>>>> done unless an equal sign was in there somewhere; confused a formula
>>>> and an equation; and completely fucked up the definitions of the
>>>> first, second and third derivatives? Amongst many other of his
>>>> hilarious fuckups. LOL
>
>>>>>>> You can't fake knowing math.
>
>>>>>> Says the guy who fucked up above. LOL
>
>>>>> Actually, no, it was you who over-enthusiastically took the second
>>>>> derivative when all we were dealing with were first derivatives.
>
>>>> Ok, so I went over your head. I'm marking you down for that. LOL
>
>>>>>>> Prediction: the response to this will be "jess trollin'".
>
>>>>>> Wrong. Again. LOL
>
>>>>> Except, see below...
>
>>>> Still wrong. Again. LOL
>
>>>>>>> And I hesitate to give a sensible answer regarding 2x for a
>>>>>>> specific point x, because _that_ does use trigonometry, but not
>>>>>>> for the reasons you think. for r = sin(theta), r is the ratio, and
>>>>>>> theta is the angle.
>>>>>>> But let's take that example of x^2 for x = 5 (picked out of thin
>>>>>>> air) and see what we get:
>>>>>>> x = 5 f(x) = (5)^2 = 25 d/dx( f(x) ) = 2x; for x = 5, this is 10
>>>>>>>
>>>>>>> So we know a few things about that point on the curve:
>>>>>>> It is at (x,y) = (5,25).
>>>>>>> The slope of the point tangent to the curve at (5,25) is 10.
>>>>>>>
>>>>>>> What is the slope? It is the ratio of y/x.
>>>>>>> So the "angle of 2x" for x=5 would be solved by using the
>>>>>>> trigonometric function that solves for y/x ratios -- arctan.
>>>>>>> (Remember tangents? This is a song about tangents.)
>
>>>>>> But we're not talking about the slope of x^2,
>
>>>>> Actually, we are. In purely mathematical terms, that's what a
>>>>> derivative is _for_.
>
>>>> And what's the derivative of x^2? Oh, it's 2x. So yet again I'm
>>>> correct. LOL
>
>>>>> Let's take the case of when you were dropped on your head as a
>>>>> child.
>
>>>> Fanfic. LOL
>
>>>>> The formula for the distance covered is d = (1/2)At^2.
>>>>>
>>>>> In english units, acceleration of Earth's gravity is approximately
>>>>> 32 ft/sec/sec. I'll leave off the units, and you can see how this
>>>>> works.
>>>>>
>>>>> d = -16t^2
>>>>>
>>>>> This is a parabola. First derivative (as you point out elsewhere)
>>>>> give velocity:
>>>>>
>>>>> s = -32t
>>>>>
>>>>> This is a straight line,
>
>>>> The equation for free-fall distance (discounting air resistance and
>>>> buoyancy effects) due to gravitational acceleration is:
>>>> y=\frac{1}{2}(9.80665\cdot x^2)
>>>>
>>>> The instantaneous velocity of a falling object due solely to
>>>> gravitational acceleration (discounting air resistance and buoyancy
>>>> effects) that has traveled distance x is:
>>>> y=\sqrt{2\cdot 9.80665\cdot \left(\frac{1}{2}\left(9.80665\cdot
>>>> x^2\right)\right)}
>>>>
>>>> Thus (taken straight from the graph):
>>>> Time: Distance Fallen: Vi:
>>>> 1 second 4.903 m 9.807 m/sec 2 seconds 19.613 m
>>>> 19.613 m/sec 3 seconds 44.13 m 29.42 m/sec
>>>>
>>>> Compare that to your equation.
>>>> Time: Distance Fallen: Vi:
>>>> 1 second 16 feet (4.9768 m) 32 feet/sec (9.7535 m/sec)
>>>> 2 seconds 64 feet (19.5072 m) 64 feet/sec (19.5072 m/sec)
>>>> 3 seconds 144 feet (43.8912 m) 96 feet/sec (29.2609 m/sec)
>>>>
>>>> <http://i.imgur.com/5fT3sCp.png>
>
>>>>> but its units are in a different frame of reference. You don't plot
>>>>> this line with the parabola and hope to see something meaningful
>
>>>> Huh, I just did. You apparently can't. LOL
>
>>>>> -- you use this resulting formula (the first derivative) to develop
>>>>> the formula that gives you a line tangent to the curve for any given
>>>>> x.
>
>>>>>> we're talking about the slope of its derivative, for which the only
>>>>>> two true conditions are [0,0] and [2,4].
>
>>>>> I'm afraid you're still confused.
>
>>>> Says the guy who can't figure out how to read a graph. Do you not
>>>> understand that the graph represents the equations, and can thus be
>>>> used to figure out the same results as the equations? Are ya skooled
>>>> yet? LOL
>
>>>>>>> arctan(10)
>>>>>>> 1.47112767430373459185287557176173085185530637718323
>>>>>>>
>>>>>>> So there's your answer in radians, Cadet Fakey.
>>>>>>>
>>>>>>> Oh, you want that in degrees?
>>>>>>> 84.28940686250035748730411865176563988852083893309440
>>>>>>>
>>>>>>> So the curve x^2 at that point (5,25) is about 6 degrees from
>>>>>>> vertical,
>>>>>>> leaning to the right...political pun not intended.
>
>>>>>> It's just as easy to graph it.
>>>>>> <http://i.imgur.com/x2Z9U7s.png>
>>>>>> <http://i.imgur.com/emGGhNA.png>
>>>>>> Gee... I got the same answers you did.
>
>>>>> No you didn't,
>
>>>> Yeah. I did. Same angle in radians and degrees as you got. LOL
>
>>>>> you graphed formulas that are only orthogonally related to each
>>>>> other.
>
>>>> I got the correct answers. Again. LOL
>
>>>>> Let me show you what it looks like closer to the origin:
>>>>> x = 3 f(x) = x^2 so for the point in question, you have (3,9)
>
>>>> That's exactly what I got. LOL
>>>>
>>>> <http://i.imgur.com/sO60qV6.png>
>
>>>>> d/dx(f(x)) = 2x so the slope of the line tangent to the curve at
>>>>> (3,9)
>>>>> is 6.
>
>>>> That's exactly what I got. LOL
>>>>
>>>> <http://i.imgur.com/sO60qV6.png>
>
>>>>> But that is the slope of the line _that passes through 3,9_. So the
>>>>> formula for _that_ line -- the line that would make sense to graph
>>>>> with it -- is
>>>>>
>>>>> [ insert here: you know the formula for the line of a given slope
>>>>> is y=mx+c, I hope, where "m" is the slope. If not, then welcome to
>>>>> first semester algebra.]
>>>>>
>>>>> y = 6x + c, where "c" is some constant to make the line pass through
>>>>> (3,9). (That is to say, the value of y when x=0).
>>>>>
>>>>> So solve for c:
>>>>>
>>>>> 9 = 6(3) +c c = -9
>>>>>
>>>>> So the line that makes sense to plot with the parabola is:
>>>>> y = 6x-9
>>>>>
>>>>> *NOW* you can start plotting:
>>>>> http://imgur.com/PMbfGPj
>>>>>
>>>>> The _line_ I plotted is tangent to the curve at (3,9). It passes
>>>>> through (3,9), and it's "parallel" (instantaneously) at that point.
>>>>>
>>>>> All the derivative gives you is the _slope_ of the line I plotted --
>>>>> but you still need to figure out the formula for the line, and that
>>>>> changes from point to point.
>>>>>
>>>>> _That_ is how you use a derivative. Look at the graph. Do you see
>>>>> now?
>
>>>> And that gives 80.538 degrees, or 1.40565 radians, at that point.
>>>>
>>>> <http://i.imgur.com/a1KIqCN.png>
>>>>
>>>> Gee... I was right. Again. Why can't you read a graph? Are ya skooled
>>>> yet? LOL
>
>>>>>> Seems I have an intuitive grasp on the mechanics and the
>>>>>> mathematics of it,
>
>>>>> I'm afraid not, you just plotted a bunch of functions that were
>>>>> orthogonally related, but not the line that would have been obvious
>>>>> to plot, given what a derivative is _for_.
>>>>>
>>>>> Unless you can come up with some kind of utility to plotting the
>>>>> line indicated by the formula that gives you the slope of a line
>>>>> tangent to the curve at a given point, I'd have to say you're
>>>>> utterly at sea.
>
>>>> Is that why I've gotten it right twice now, with even greater
>>>> accuracy than you could manage in the second instance? LOL
>
>>> AS IF YOU DIDN'T JUST GOOGLE "DERIVATIVE" AND THEN POAST YER RESULTS.
>>>
>>> lolol
>>>
>>> OLOOL
>>>
>>> LOL
>
> You're awfully melty, DildoRider... is it because I've demonstrated that
> I'm right three times now? Despite Scott claiming otherwise, I've gotten
> the same results he did... apparently he doesn't understand that the
> graph represents the equations, thus the same information can be gleaned
> from the graph as can be from the equations. But he apparently can't
> read a graph. LOL
>
>> That's about the size of it.
>>
>> His graph:
>>
>> http://i.imgur.com/sO60qV6.png
>
> Yes, my graph, in which I got the same results as you. LOL
>
> Don't forget the second one, in which I got the correct angle in
> degrees:
>
> <http://i.imgur.com/a1KIqCN.png>
>
>> The graph that he apparently didn't look at:
>>
>> http://imgur.com/PMbfGPj
>>
>> Apparently, he doesn't get it.
>>
>> for f(3) = x^2
>>
>> d/dx(x^2) = 2x m = 2x = 2(3) = 6
>>
>> So we have the slope, m.
>>
>> y = mx+c 9 = 6(3) + c c = -9
>>
>> So we have the constant.
>>
>> y = 6x-9
>>
>> So we have the formula for the line tangent to the curve x^2 at x=3.
>>
>> http://imgur.com/PMbfGPj
>>
>> Checks out.
>
> As does mine. In fact, the second one I did was even more accurate than
> your equations. Are ya skooled yet? LOL
>
>> Anything else is chinese room mathematical word salad.
>
> Is that why I'm getting the correct answers, Scott? Or is it just a case
> of you being unable to read a graph? LOL
You can declare "victolly" all you like, but you haven't displayed any
knowledge of the process. You've posted some graphs that are only
orthogonally related to the answer. This is spaghetti against the wall.
If not, then please show me where you posted the equation for the line
tangent to the curve at any point "x". I've used x=3 for my example
because it's easy to graph, but you can use any other point.
All you've done is plot slopes, which is not the entire answer. Put them
to use.
If you plot the curve and the line tangent to the curve, it should look
like this:
http://imgur.com/PMbfGPj
I'm going to assume you understand the graph, because it's dead-simple.
And I have no doubt that you can do this, if you simply apply yourself to
picking a point on the curve, and showing the equation for the line
tangent to the curve at that point. I've shown you how to do this -- and
if I can do it, then you can too.
--
Won a Checky(tm) on 2016-04-15
...for schooling a kook about derivatives.
(Including working through a sample problem.)
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Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-13 06:58 +0200
Re: Our very own "chinese room" "\"Fakey's\" dogwhistle holder living at 5907 Stanton Ave., Pittsburgh, PA (aka Teh Mop Jockey), socked up as 5907 Stanton Avenue, Pittsburgh, PA 15206-2117" <root@127.0.0.1> - 2016-04-13 01:20 -0400
Re: Our very own "chinese room" Skeet <invalid@invalid.invalid> - 2016-04-13 13:23 -0600
Re: Walking through a problem that uses a derivative Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-16 07:38 +0200
Re: Walking through a problem that uses a derivative vallor <vallor@cultnix.org> - 2016-04-16 14:48 +0000
Re: Walking through a problem that uses a derivative Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-17 07:35 +0200
Re: Walking through a problem that uses a derivative "\"Fakey's\" dogwhistle holder living at 5907 Stanton Ave., Pittsburgh, PA (aka Teh Mop Jockey), socked up as 5907 Stanton Avenue, Pittsburgh, PA 15206-2117" <root@127.0.0.1> - 2016-04-17 01:50 -0400
Re: Walking through a problem that uses a derivative vallor <vallor@cultnix.org> - 2016-04-17 18:08 +0000
Re: Walking through a problem that uses a derivative Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-18 07:29 +0200
Re: Walking through a problem that uses a derivative vallor <vallor@cultnix.org> - 2016-04-18 06:24 +0000
Re: Walking through a problem that uses a derivative Rick Sabian's Allstar Canadian Assworm Zydeco Band <Lunatic.Fringe@The.Edge> - 2016-04-17 23:28 -0700
Re: Walking through a problem that uses a derivative Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-19 08:28 +0200
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-16 07:58 +0200
Re: Our very own "chinese room" Rick Sabian's Allstar Canadian Assworm Zydeco Band <Lunatic.Fringe@The.Edge> - 2016-04-16 00:01 -0700
Re: fakeys meltdown Skeet <invalid@invalid.invalid> - 2016-04-16 02:27 -0600
Re: Our very own "chinese room" "\"Fakey's\" dogwhistle holder living at 5907 Stanton Ave., Pittsburgh, PA (aka Teh Mop Jockey), socked up as 5907 Stanton Avenue, Pittsburgh, PA 15206-2117" <root@127.0.0.1> - 2016-04-16 11:22 -0400
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-17 06:56 +0200
Re: Our very own "chinese room" "\"Fakey's\" dogwhistle holder living at 5907 Stanton Ave., Pittsburgh, PA (aka Teh Mop Jockey), socked up as 5907 Stanton Avenue, Pittsburgh, PA 15206-2117" <root@127.0.0.1> - 2016-04-17 01:20 -0400
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-18 07:19 +0200
Re: Our very own "chinese room" Janithor <Janithor@comcast.net> - 2016-04-16 23:06 -0700
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-16 08:15 +0200
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-17 07:40 +0200
Re: Our very own "chinese room" "\"Fakey's\" dogwhistle holder living at 5907 Stanton Ave., Pittsburgh, PA (aka Teh Mop Jockey), socked up as 5907 Stanton Avenue, Pittsburgh, PA 15206-2117" <root@127.0.0.1> - 2016-04-17 01:53 -0400
Re: Our very own "chinese room" Friendly Neighborhood Vote Wrangler Emeritus <FNVWe@altusenetkooks.xxx> - 2016-04-18 07:04 +0200
Re: Our very own "chinese room" Skeet <invalid@invalid.invalid> - 2016-04-17 23:56 -0600
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