# Search results

1. ### Polarity of a molecule

Well, I know how to add vectors but only if they're 2d...
2. ### Polarity of a molecule

Hi, I know what are the steps to determine if a molecule is polar or not, but I'm having one small problem. When I have determined teh geometrical shape of my molecule and drew the vectors of the polar bonds that goes from the least electronegative atom to the most electronegative atom, how...
3. ### Notation question

Yes, I also noticed it. Ok, thank you!
4. ### Notation question

But shouldn't we say : y --> -2^(-) and not y --> 2^(-) ?
5. ### Notation question

Hi, I have a question about : http://imgur.com/RU7PvtJ I actually understand what I need to do. I need to see if both one sided limits are the same to establish that the limit exists. The only thing which I just find weird is the "since y --> 2^(-) implies y<-2" Can somebody explain me...
6. ### Question about limit fact

Nah, its okay, no need for that anymore.
7. ### Question about limit fact

I was wondering, when we consider several functions at once in the same graph, is it ok if this whole is not a function itself ? Do we care about whether this whole is function or not ?
8. ### Question about limit fact

Hi, I'm having trouble understanding the following fact about limits : If f(x)<=g(x) for all x on (a,b) (except possibly at c) and a<c<b then, lim f(x) <= lim g(x) x -> c x->c Here's how I interpret the definition : We have two functions f(x) and g(x), and the inequality f(x)<=g(x)...
9. ### Euclid's element (P14)

I don't think I understand your explanation... Didn't Euclid "prove" with proposition 13 that the sum of two angles were equal to two right angles ? And that we begin the demonstration assuming that the sum of the angle CBA and ABD were equal to two right angles ? What role does postulate 4 play...
10. ### Euclid's element (P14)

http://aleph0.clarku.edu/~djoyce/java/elements/bookI/propI14.html Hi, I was reading proposition 14 of Euclid's elements and there is only one thing which I find weird : why do we need postulate 4 to conclude that " the sum of the angles CBA and ABE equals the sum of the angles CBA and ABD."...
11. ### A null set is a subset of every set

Well, I do understand your first part. Now, for the second part, are you saying that because the empty set has no elements, it can't satisfy(be a subset) of B?
12. ### A null set is a subset of every set

Hi, I was wondering, how can a null set be a subset of other sets? Could anyone explain the idea in non technical terms, I'm just a beginner. :) Thank you!
13. ### COmbination problem

Ok, Thank you again. I didn't know the standard way...^^
14. ### COmbination problem

Well, we need two different sorts, so we have a total combination of 9 for 10 different flavour. For example, if we consider each flavour a number, then : (1,2) (1,3) ... til (1,10) Now, if we want to see for the second flavour, we already did the combination (1,2), so we must substract 1...
15. ### COmbination problem

Hi, An ice cream shop sells ten different flavors of ice cream. You order a two- scoop sundae. In how many ways can you choose the flavors for the sundae if the two scoops in the sundae are different flavors? That's what I did : 9+(9-1)+(9-2)+...+(9-9)=45 Would this be any good ...
16. ### Manometer question

Hi, Just have a basic question on a closed manometer : http://postimg.org/image/6tq089eoz/ So I do understand the basic idea behind manometers. I see that in this case the pressure of gas is lower than that of the liquid, which is why the liquid is higher on the left side. Now, what I...
17. ### Question about kinetic energy

Hi, I was wondering, how is it possible that different gases can have the same average kinetic energy?(at same temperature) Can anybody give me a SIMPLE explanation of this? Knowing that some particles will move faster than others, I wonder how this can be possible :/ It would really help ...
18. ### Kinetic energy of gas

I don't know any calculus :/ But is my interpretation any good??
19. ### Kinetic energy of gas

Well, if the temparture gets higher the molecules tend to move faster and produces more kinetic energy.Atleast, that's what I understood from reading my things...
20. ### Kinetic energy of gas

Two identical bottles contain the same number of molecules at ambiant conditions of temperature and pression.The first contains N2, and the second CO2.Tell if the it's true/false and explain why The molecules of CO2 have more kinetic energy than the molecules of N2. My answer : False...
21. ### Chemical transformation (Decomposition)

Hi, I was wondering when you need to write the decomposition of a substance, how do you know if the number is going to be a coefficient or subscript ? Example: 2H2O ===>2H2 + 02 would be the answer But why not 2H2O ==> 2H2 + 2O Knowing that we have 2 moles of O in the beginning...
22. ### Motion of objects

Yeah, it makes more sense. Thanks for the correction!
23. ### Motion of objects

To be frank, I did not expect it at all... it makes me quite ashamed ^^
24. ### Motion of objects

I've been suggested that it's a cycloid. Btw are the other two correct ? thank you
25. ### Motion of objects

Hi, I have begun physics and we are seeing systems of reference as an introduction.Now I have a small exercise which I'm not sure of, I would need you to check if it's correct or not. There are two cyclists A and B. Suppose that you take place on a sidewalk and look at them pass. They move to...
26. ### Proof of ax=a then x=1

No need to answer, I understand now. THank you!
27. ### Proof of ax=a then x=1

-Wait, what do you mean that my rules won't result in a*a^-1*x= a*a^-1 ? Is it only because I've put a^-1 in the middle that it isn't correct ? -The way I thought about the proof was to justify that it would work wether we were talking about positive numbers or negative numbers, hence the the...
28. ### Proof of ax=a then x=1

I haven't written a lot of proofs so I need the opinion of the experts on my proof of a simple proposition. Here's the various properties I used: (P10) (Trichotomy law) For every number a, one and only one of the following holds: (i) a = 0, (ii) a is in the collection P, (iii) —a is in the...
29. ### Proof of neighbor fractions

Ok, sorry for being late to respond : a/b-c/d=+-1/bd xi/xj-c/d (to be determined) +-1/((xj)*d) (i/j-c/d(to be determined)+-1/xj*d) * jd id-jc not equal to +-1/x except for 1 and -1 The same is done for the second fractions on the left side.
30. ### Triangle inequality proof in Spivak's calculus

Well, I have another question. When Spivak justifies the passage from the squares to |a+b| <= |a|+|b| he says the following : x^2<y^2 supposes that x<y for x,y in N. Now, the only thing bugging me is the following : Why didn't he do the following x^2<=y^2 supposes that x<=y for x,y in N ...
31. ### Triangle inequality proof in Spivak's calculus

No need to answer, it's understood !
32. ### Triangle inequality proof in Spivak's calculus

So hi, there's one little thing which I'm not understanding in the proof. After the inequality Spivak considers the two expressions to be equal. Why?!? I just don't see why we can't continue with the inequality and when we have factorized the identity to (|a|+|b|)^2 we can just replace...
33. ### Proof of neighbor fractions

Ah ok, then I'll post here my new finding when I create the other part of the proof. I just didn't follow the following : but this exception corresponds to irreducible fractions, so it's fine (as long as you consider it in this way) Could you rephrase ? (I'm tired, so maybe I'm not reading...
34. ### Proof of neighbor fractions

Wait, what do you mean I considered only one case ? I tried to consider two factorizable fractions at the sametime... Also, for the special case you were talking about, I did notice that there was an exception but I rejected it, didn't think it would have great consequence. Is it the following...
35. ### Proof of neighbor fractions

*If I turn out to have a wrong answer, please no hints or showing an valid proof. I want to do it on my own ! ad/bd-bc/bd=+-1/bd is neighbor fraction Now, reduce the common numbers : a/b-c/d=+-1/bd We must now prove that the left hand side has irreductible fractions. Let's see what...
36. ### Basic question on spivak's calculus

Yeah, I noticed that. I just was expecting the inverse, the factorization. Anyway, thank you for the help!
37. ### Basic question on spivak's calculus

Yeah, that I understood. The other thing which I don't understand is why does he talk about using P9 to factorize if he's showing the development of factors. How does it make any sense ?thank you!
38. ### Basic question on spivak's calculus

http://postimg.org/image/lh7ga876t/ [Broken] Hi, I have a basic question concerning definition of the word 'factorization'. Does Spivak consider factorization as development of factors ? He goes from saying the "factorization" x2−3x+2=(x−1)(x−2) is really a triple use of P9 and goes on...
39. ### Proof on angles.

Ok, thanks for the info !
40. ### Proof on angles.

http://postimg.org/image/3mmlbro1p/ [Broken] Hi, I just want to know if my proof seems ok. So we can begin with : 1 degrees = 1+1/9 grads we multiply by x to generalize x degrees= x+x/9 grads now, we take x degrees and multiply it by 60 minutes to know how many minutes it makes.We also do...
41. ### Right angle triangle problem

Yes, it's working ! Those are the times when I feel really ashamed of myself for doing stupid errors like this one -_____- Thank you agian!
42. ### Right angle triangle problem

Oh,wow, I just noticed my error!(With the 10) Thank you ! Thats why I was getting a wrong answer !

44. ### Right angle triangle problem

The number of degrees in one acute angle of a right-angled triangle is equal to the number of grades in the other; express both the angles in degrees. So I have found the following answers : 810/17=47,05... degrees and 810/17=47,05... grades which gives 42,35... degrees Now, the real answer...
45. ### SImple proof question

Yeah, I didn't understand it in the correct way. Thank you !
46. ### SImple proof question

I'm studying Spivak's calculus and I have a really simple question : I'm only in the first chapter on "The basic properties of numbers" So far, we have the following propostion P1 : (a+b)+c=a+(b+c) P3 : a+(-a)=(-a)+a=0 P2 : a+0=0+a=a Now, he tries to prove P2 (He doesn't do it...
47. ### Conversion problem.

How do you convert angles from the sexagecimal system to centesimal one ? For example 63 degrees 14 minutes 51 seconds reduced to centesimal ?? Here's how it's done but I don't understand the steps... http://postimg.org/image/4tat51y63/ Thank you
48. ### Vector question

Ok, I thouht that there was a major difference between the two of them. thank you
49. ### Vector question

Hi, I'm learning vectors and there's two notions which I don't distinguish : Is the orientation of a vector (determined by the angle it has) the same thing as the direction of a vector ? thank you
50. ### Trigonometry question

Could you develop please ?I know arcsine... ( btw, it's from 0 to 2pi for the solutions)