Topic aide bahut en tout genre :D (repaire des glandeurs)

iamaseb, je t'ajoute à mon MSN, on parlera directement

Coucou

Un autre petit problème, celui qui arrive me résoudre ca gagne une partie de mon estime eternelle


On est dans l'espace euclidien en 3D, avec un repere orthonormé direct, et 4 points A B C D non coplanaires

Il faut trouver :

S = {M € E3 | (MAxMB) x (MCxMD) = 0 }

Où MA MB MC et MD sont des vecteurs, et les x des produits vectoriels.

Merci.

rapidement sans me prendre la tete.
le X au milieu, c'est pas une simple multiplication plutot qu'un produit vectoriel? Y a pas de conditions sur les points?
sinon il suffit de montre que MAxMB=0 ou MCxMD=0 soit les angles AMB=90° ou CMD=90°
en faisant le calcul en prenant les coord des pts, ca marche pas?

beenie, tu m'épates ! (même si, vu que j'ai rien compris, je ne peux dire si tu as juste)

iamaseb, j'ai pas donné de reponse. Juste qq explications (mais c'est peut etre des betises)

ca me semble bizarre car ce qu'on doit demontrer que les plans comprenant respectivement A, B et C, D sont "perpendiculaires" or si la seule condition est A, B, C, D non coplanaires, ca me semble pas possible

Coucou

Un autre petit problème, celui qui arrive me résoudre ca gagne une partie de mon estime eternelle


On est dans l'espace euclidien en 3D, avec un repere orthonormé direct, et 4 points A B C D non coplanaires

Il faut trouver :

S = {M € E3 | (MAxMB) x (MCxMD) = 0 }

Où MA MB MC et MD sont des vecteurs, et les x des produits vectoriels.

Merci.

rapidement sans me prendre la tete.
le X au milieu, c'est pas une simple multiplication plutot qu'un produit vectoriel? Y a pas de conditions sur les points?
sinon il suffit de montre que MAxMB=0 ou MCxMD=0 soit les angles AMB=90° ou CMD=90°
en faisant le calcul en prenant les coord des pts, ca marche pas?

Non c'est bien des produits vectoriel, des 'v' à l'envers quoi
La seule condition c'est A B C D non coplanaires

:lol: au temps pour moi
j'ai confondu "produit vectoriel" et "produit scalaire"
oublie tout ce que j'ai dit
par le calcul, ca devrait passer

Tu es en quoi vassili ??

On est dans l'espace euclidien en 3D, avec un repere orthonormé direct, et 4 points A B C D non coplanaires

Il faut trouver :

S = {M € E3 | (MAxMB) x (MCxMD) = 0 }

Où MA MB MC et MD sont des vecteurs, et les x des produits vectoriels.

ça fait super longtemps que j'en ai pas fait, mais j'ai l'impression que l'ensemble que tu cherches n'existe pas.

Car :
Tes vecteurs (MAxMB) et (MCxMD) doivent être colinéaires pour que leur produit vectoriel soit égal au vecteur nul.

(MAxMB) est orthogonal au plan MAB et (MCxMD) est orthogonal au plan MCD.

A,B,C,D sont non coplanaires donc les plans MAB et MCD ne sont pas parallèles, ils sont sécants. Donc (MAxMB) et (MCxMD) ne peuvent être colinéaires.

Voilà ptet que je me suis gouré qqpart, faudrait qu'Anh Thom passe par ici pour confirmer...

fourcroy est demandé d'urgence sur ce topic

The world we’re leaving in is complex. Human being, the most intelligent species do know lot’s of thing. They create chemicals from raw material.


But sometimes we’re doing things that we do not know the consequence of it. Like asbestos, if at first it sounds great, we now know that it is really harmful for human being. When we came with genetically modified food, in order to increase crop, we did not think about the consequences.

We produce so much that there is environmental issues.

The human body along with different species, animal and vegetal can’t survive with our action. The number of extinct species sky rocket and it will continue if nothing is done. American and Canadians scientists explain recently that almost all of the fish and crustaceans that we’re fishing for consummation will extinct from the ocean before 2050 if currents trends continue.

Global warming is the reason why we’re all in danger. But, we are responsible for the global warming.

Our car, plants, house … release toxic gases. There is toxic waste everywhere, and the only thing we do about it is to landfill them in the ground. Our way of live requires huge consummation of raw material like fossil fuel, wood … and the waste is not helping.
Deforestation as long with toxic emanations disrupts wildlife.
Release of toxic gases is the reason why green effect is so important. The ozone layer is falling apart, which explain the global warming. We can see with our eyes the rising sea levels due to glacier meltdown. Shores are different from before. Earthquake, storm can be explain by the global warming, meaning that the global warming have already killed million of human throughout the world.

What should we do about it?

It is easy and difficult at the same time. We all know that exhaust fumes are harmful, so we could stop using oil for our car, house central heating … But we still have to find energy. Nuclear is one of them, but there is radioactive fallout, and it seems like there is nothing to do about it nowadays.
But, we are in the situation where the difficulty is not an excuse anymore. Yes, there will be some cost to make if we want a future. Sustainability is not an easy thing, it need efforts. But, we are the species that have been capable of produce very small engine that can kill million; we should be able to stop producing and selling disposable goods, or at least make sure they are biodegradable.

We should ask ourselves if we can survive if nothing is changed in our way of thinking, our values …

We should all be environmentalist!
Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.
The prevailing scientific opinion on climate change is that "most of the warming observed over the last 50 years is attributable to human activities".
The increased amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) are the primary causes of the human’s warming activities.
An increase in global temperatures can cause changes like a rising sea level.
These changes may increase the frequency and intensity of extreme weather events, such as floods, heat waves, hurricanes, and tornados.
The term "global warming" is a specific case of the more general term "climate change" .In principle, "global warming" is neutral as to the causes, but in common usage, "global warming" generally implies a human influence.
The detailed causes of this change remain an active field of research, but the scientific consensus identifies greenhouse gases as the primary cause of the recent warming.
Various alternative hypotheses have been proposed to explain all or part of the observed increase in global temperatures, including but not limited to:
• The warming is the consequence of natural variation.
• The warming is a consequence of the end of a former cool period — the Little Ice Age.
• The warming is primarily a result of variances in solar irradiance, possibly via modulation of cloud cover
• The warming actually reflects the urbanization as more and more populated areas are expanding with growing population.
The predicted effects of global warming are many and various, both for the environment and for human life. These effects include sea level rise, impacts on agriculture, reductions in the ozone layer, increased intensity and frequency of extreme weather events, and the spread of disease. In some cases, the effects may already be manifest, although it is difficult to attribute specific natural phenomena to long-term global warming. In particular, the relationship between global warming and hurricanes is still being debated.



Quelqu'un pour corriger les trop grosses fautes

Juste la première phrase : c'est pas "living" (vivre) que tu voulais mettre à la place de "leaving" (quitter) ?
Désolé si je me suis trompé...

Ca fait aussi des années que je ne fais plus de géométrie... Cela dit, je suis a priori sur la même ligne que Tactao. Je ne vois que les solutions triviales M confondu avec l'un des points A,B,C, ou D... Ou alors Vassili a mal recopié son énoncé et le produit vectoriel du milieu est un produit scalaire...

Tactao, moi?:lol: ca fait qques années que j'ai pas touché à la géométrie, et j'ai jms été très fort en géométrie, mais ce que tu dis n'est pas faux, et ca doit même etre la réponse

Vassili, et alors, c'est quoi la solution ?

Dagobert, ah ouais, elle est belle cette faute
Mais j'ai changé tout le début pour que ce soit un peu plus anglais :

Introduction


For the first time, a species, human beings have into their hand the future of the planet.
We are living in a complex world, a world that existed before us, and should have existed after us.
We are the most intelligent species of all time. We create cities, cinema, computing, lots of unnecessary goods …we create chemicals from raw material.

We have done so much during last decades that sometimes we ask ourselves if it’s real or not. But what is real is that we did not think about the consequences of our choice, about the consequences of the so call “progress”.

Like asbestos, if at first it sounds really interesting, we now know that it is really harmful for human being. We will say the same about genetically modified food, developing in order to increase crop, we don’t think about the consequences.

Human produce so much that there is environmental issues.

The human body along with different species, animal and vegetal seems to be suffering from human action. The number of extinct species have sky rocketed and it will continue if nothing is done. Americans and Canadians scientists have explained recently that almost all of the fishes’ and crustacean’s species that we fish for consummation will extinct from the ocean before 2050 if currents trends continue.

Global warming is the reason why our species is endangered along with others. But as we will see, we are responsible for global warming.


Our standard of living, such has having car, living the night with lights… is responsible for mass toxic gases released. There is toxic waste everywhere, and the only thing we can do about it is to landfill them in the ground. Indeed, our way of live requires huge consummation of raw material like fossil fuel, wood … and because of our lack of awareness, we waste a lot.


There is consequence to that:
• Deforestation as long with toxic emanations disrupts wildlife.
• Release of toxic gases is the reason why green effect is so important. The ozone layer is falling apart, because of that global warming is more important. We can see with our own eyes the rising sea levels due to glacier meltdown. Shores are different from before. Earthquake, storm comes from global warming, meaning that global warming have already killed millions and millions human lives throughout the world.

What should we do about it?

It is easy and difficult at the same time. We all know that exhaust fumes are harmful, so we could stop using oil for our car, house central heating … But we still have to find energy. Nuclear is one of them, but there is radioactive fallout, and it seems like there is nothing to do about it nowadays.
But, we are in a situation where difficulties are not an excuse anymore. Yes, there will be some cost to make if we want a future. Sustainability is not an easy thing, it need efforts and sacrifices.
But when we think about what we have done, we should be able to stop producing and selling disposable goods, or at least make sure they are biodegradable.
We daresay we can already do that. We already know how to make thing better, but we’re not doing it. The problem is elsewhere, can we change our way of thinking? Forget about profit?
Forget about what we learned?


Yes, we have designed high tech apparatus, we have developed complex system, but in the end it’s like we were unable to change our way of life even when self-preservation is at stake. Animal can do that, and yet we, the smartest species of all time, fail to do that.




What is global warming?

Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.
The prevailing scientific opinion on climate change is that "most of the warming observed over the last 50 years is attributable to human activities".
The increased amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) are the primary causes of the human’s warming activities.
An increase in global temperatures can cause changes like a rising sea level.
These changes may increase the frequency and intensity of extreme weather events, such as floods, heat waves, hurricanes, and tornados.
The term "global warming" is a specific case of the more general term "climate change" .In principle, "global warming" is neutral as to the causes, but in common usage, "global warming" generally implies a human influence.
The detailed causes of this change remain an active field of research, but the scientific consensus identifies greenhouse gases as the primary cause of the recent warming.
Various alternative hypotheses have been proposed to explain all or part of the observed increase in global temperatures, including but not limited to:
• The warming is the consequence of natural variation.
• The warming is a consequence of the end of a former cool period — the Little Ice Age.
• The warming is primarily a result of variances in solar irradiance, possibly via modulation of cloud cover
• The warming actually reflects the urbanization as more and more populated areas are expanding with growing population.
The predicted effects of global warming are many and various, both for the environment and for human life. These effects include sea level rise, impacts on agriculture, reductions in the ozone layer, increased intensity and frequency of extreme weather events, and the spread of disease. In some cases, the effects may already be manifest, although it is difficult to attribute specific natural phenomena to long-term global warming. In particular, the relationship between global warming and hurricanes is still being debated.

Ca fait aussi des années que je ne fais plus de géométrie... Cela dit, je suis a priori sur la même ligne que Tactao. Je ne vois que les solutions triviales M confondu avec l'un des points A,B,C, ou D... Ou alors Vassili a mal recopié son énoncé et le produit vectoriel du milieu est un produit scalaire...

Les droites CD et AB sont solutions (si M est sur AB alors MA et MB sont colinéaires donc le produit vectoriel des 2 est nul). Et je ne vois pas trop ce qu'il pourrait y avoir en plus si les points ne sont pas coplanaires mais bon, c'est pas une preuve
On peut-être tenter d'utiliser la formule du double produit vectoriel mais je l'ai plus en tête.

PS : Moi non plus, c'est pas mon dada, ce genre de géométrie

Nosco, tu as raison, bien sûr ; il n'y a peut-être que les solutions triviales... mais elles sont plus nombreuses qu'annoncées.

Je préfère la théorie de la mesure.

Je suis beaucoup plus fort en cuisine qu'en solution triviales ou autres vecteurs colinéaires qui restent ma foi assez simple devant mon Anglais

Je préfère la théorie de la mesure.

C'est ce que je préfère dans les cours mathématiques de début d'année (il faut dire que l'algèbre générale, la topologie et le calcul différentiel... )

ca me rappelle la pire année scolaire de ma vie : le deug mias

Chers OMlivers, j' ai un petit problème et je me permet de solliciter votre aide, je m'explique.
Je dois faire une revue de presse internationale en anglais.
J'ai choisit le sujet de la condamnation de saddam à travers trois articles: un anglais, un français et un américain. Jusque là tout va bien mais j'ai un seul problème, c'est que je voudrais illustrer tout ca grace à une petite vidéo (style reportage d'un JT anglais) à montrer à la classe sur ce sujet.
Même en cherchant bien sur google et compagnie, je n'ai pas trouvé de vidéos téléchargables, je n'ai eu que des vidéos consultables en ligne.
Ca serait cool si quelqu'un pourrait me trouver une petite solution ou un lien cool pour que je puisse en télécharger une en toute légalité, merci d'avance