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maximR
post Dec 13 2013, 11:02 PM

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QUOTE(v1n0d @ Dec 13 2013, 11:01 PM)
You mean disprove. Yes, by providing a counterexample.
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Okay . Thank you ! icon_rolleyes.gif
RED-HAIR-SHANKS
post Dec 13 2013, 11:04 PM

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QUOTE(v1n0d @ Dec 13 2013, 10:56 PM)
The product of irrationals aren't always rational. As with the original question, one only need show an example to prove this statement true.
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Oh, thanks for your clarification.
But, again, does this proof is constructive since √2^√3, and that the results is irrational?
v1n0d
post Dec 13 2013, 11:07 PM

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QUOTE(RED-HAIR-SHANKS @ Dec 13 2013, 11:04 PM)
Oh, thanks for your clarification.
But, again, does this proof is constructive since √2^√3, and that the results is irrational?
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I don't quite understand this bit. Mind rephrasing the question?
RED-HAIR-SHANKS
post Dec 13 2013, 11:18 PM

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QUOTE(v1n0d @ Dec 13 2013, 11:07 PM)
I don't quite understand this bit. Mind rephrasing the question?
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I'm sorry, my bad. What I want to point out was that, do we only need to show just one example/proof to imply that the statement is true or false?
Like in the case of a^b, and that both a and b is irrational(suppose that both a and b is √2). And that if we multiply (a^b)^√2, we will get 2, which is rational.
But on the other hand, if a=√2, and that b=√3, the results will surely be irrational. Now, doesn't both examples contradict each other? So, how does one tell or pick one of these examples that will proof that the statement is true? unsure.gif

This post has been edited by RED-HAIR-SHANKS: Dec 13 2013, 11:22 PM
TSCritical_Fallacy
post Dec 13 2013, 11:39 PM

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QUOTE(RED-HAIR-SHANKS @ Dec 13 2013, 11:18 PM)
I'm sorry, my bad. What I want to point out was that, do we only need to show just one example/proof to imply that the statement is true or false?

Like in the case of a^b, and that both a and b is irrational(suppose that both a and b is √2). And that if we multiply (a^b)^√2, we will get 2, which is rational.

But on the other hand, if a=√2, and that b=√3, the results will surely be irrational. Now, doesn't both examples contradict each other? So, how does one tell or pick one of these examples that will proof that the statement is true?
I'm back! Wow, what a fruitful discussion... laugh.gif

In logic, accordingly, the statement “There exist irrational numbers a and b such that a^b is rational” means “At least one, but not all cases, where two irrational numbers a and b will produce a rational value of a^b.icon_idea.gif

This post has been edited by Critical_Fallacy: Dec 13 2013, 11:39 PM
RED-HAIR-SHANKS
post Dec 14 2013, 12:51 AM

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QUOTE(Critical_Fallacy @ Dec 13 2013, 11:39 PM)
I'm back! Wow, what a fruitful discussion... laugh.gif

In logic, accordingly, the statement “There exist irrational numbers a and b such that a^b is rational” means “At least one, but not all cases, where two irrational numbers a and b will produce a rational value of a^b.icon_idea.gif
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Ok, now I got it, forgive me for my total ignorance. I would like to thank v1n0d too for helping me to delve into the question.
TSCritical_Fallacy
post Dec 14 2013, 01:00 AM

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QUOTE(maximR @ Dec 13 2013, 10:15 PM)
Call me a nerd, but this is much more exciting than a lot of things I've seen !
QUOTE(v1n0d @ Dec 13 2013, 10:15 PM)
The solution makes use of the Gelfond-Schneider theorem. smile.gif
Correct, but what happens when a≠b?
QUOTE(RED-HAIR-SHANKS @ Dec 13 2013, 10:52 PM)
But, if in the case of √2*√3, I don't think the result is rational. Correct me if I'm wrong though.
Appreciate v1n0d's efforts in guiding both of you. notworthy.gif

The whole idea is to develop your HOTS, even without the knowledge of Gelfond-Schneider Theorem.

The simplest irrational number we know is √2. So, in the simplest form, we have user posted image.

However, we do not know whether user posted image is rational or irrational. Thus, we have two cases here.

CASE 1: If user posted image is rational, then it is self-evident that the theorem is correct because both a and b are irrational from the beginning.

CASE 2: If user posted image is irrational, then we can reassign user posted image and raise it to the power of user posted image, so that user posted image, that is obviously rational, which in turn proves the theorem is correct.

CONCLUSION: Therefore, whichever the case is, we can deduce that the theorem is readily in a position to be validated, even when a ≠ b, or having two distinct irrational numbers, e.g. user posted image.

P.S.: Gelfond-Schneider Theorem only tells you that user posted image is irrational.

This post has been edited by Critical_Fallacy: Dec 14 2013, 01:16 AM
TSCritical_Fallacy
post Dec 14 2013, 01:39 AM

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QUOTE(maximR @ Dec 13 2013, 10:04 PM)
Euler’s Identity, as Sal Khan of KhanAcademy put it, 'If this doesn't blow your mind , you have no emotion.', in his long derivation of this identity. I think it involves some series but I can't recall. blush.gif
The most compact equation in all of mathematics is surely Euler’s Identity, or user posted image.

In this equation, the five fundamental constants coming from four major branches of classical mathematics – arithmetic (0, 1), algebra (i), geometry (π) , and analysis (e) , – are connected by the three most important mathematics operations – addition, multiplication, and exponentiation – into two non-vanishing terms.

Some of my Tutorial followers (in Complex numbers) are probably aware that Euler’s Identity is but one of the consequences of the miraculous Euler formula user posted image, because when user posted image, user posted image, user posted image, it follows that user posted image.

This post has been edited by Critical_Fallacy: Dec 14 2013, 01:39 AM
v1n0d
post Dec 14 2013, 08:49 AM

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QUOTE(RED-HAIR-SHANKS @ Dec 13 2013, 11:18 PM)
I'm sorry, my bad. What I want to point out was that, do we only need to show just one example/proof to imply that the statement is true or false?
Like in the case of a^b, and that both a and b is irrational(suppose that both a and b is √2). And that if we multiply (a^b)^√2, we will get 2, which is rational.
But on the other hand, if a=√2, and that b=√3, the results will surely be irrational. Now, doesn't both examples contradict each other? So, how does one tell or pick one of these examples that will proof that the statement is true? unsure.gif
*
Sorry, I slept off last night. sweat.gif
I see that Critical_Fallacy has already answered your question. laugh.gif
Michael_Light
post Dec 14 2013, 06:48 PM

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Hi! I have a question under partial derivatives, hope you can provide some clue. smile.gif

user posted image

I have no problem with part (a), but I face great difficulty with part (b) despite the hint provided by the suggested answer. I have no idea how to find user posted image.

Can you shed some light on part (b)? Thank you. rclxms.gif
VengenZ
post Dec 14 2013, 08:35 PM

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QUOTE(Michael_Light @ Dec 14 2013, 06:48 PM)
Hi! I have a question under partial derivatives, hope you can provide some clue.  smile.gif

user posted image

I have no problem with part (a), but I face great difficulty with part (b) despite the hint provided by the suggested answer. I have no idea how to find user posted image.

Can you shed some light on part (b)? Thank you.   rclxms.gif
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I'm too lazy to solve it till the end but here's a kickstart for you:
user posted image

Use product rule to solve for ∂/∂x(∂z/∂r) ..

Product rule:

user posted image

P.s: Just realised I made a silly mistake there.. notice that ∂/∂x(∂z/∂y) = ∂^2z/∂x∂y
Sorreh. icon_rolleyes.gif

This post has been edited by VengenZ: Dec 15 2013, 09:51 PM
Krevaki
post Dec 15 2013, 08:13 PM

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QUOTE(Michael_Light @ Dec 14 2013, 06:48 PM)
Hi! I have a question under partial derivatives, hope you can provide some clue.  smile.gif

user posted image

I have no problem with part (a), but I face great difficulty with part (b) despite the hint provided by the suggested answer. I have no idea how to find user posted image.

Can you shed some light on part (b)? Thank you.  rclxms.gif
*
Posting after a long hiatus:
user posted image

p/s: How's everyone doing?
maximR
post Dec 15 2013, 09:27 PM

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Done with SPM . Starting on more 'advanced' concepts for now to get used to them before PreU . How are the lecturers at USM by the way ? How 'rigorous' is the curriculum for Mech Eng ?

v1n0d
post Dec 15 2013, 09:32 PM

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QUOTE(maximR @ Dec 15 2013, 09:27 PM)
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Done with SPM . Starting on more 'advanced' concepts for now to get used to them before PreU . How are the lecturers at  USM by the way ? How 'rigorous' is the curriculum for Mech Eng ?
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USM has brought in plenty of good lecturers due to their apex status. If you're gunning for Mech Eng, I'll suggest UTM as that's their premier course. Most of the other public unis in Malaysia have adopted their syllabus and local reference material was written by lecturers there. They also have strong ties with the industry. If I remember correctly, they signed an MoU so that their Pure Mech degree is recognized by MIT.

This post has been edited by v1n0d: Dec 15 2013, 09:33 PM
maximR
post Dec 15 2013, 09:35 PM

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QUOTE(v1n0d @ Dec 15 2013, 09:32 PM)
USM has brought in plenty of good lecturers due to their apex status. If you're gunning for Mech Eng, I'll suggest UTM as that's their premier course. Most of the other public unis in Malaysia have adopted their syllabus and local reference material was written by lecturers there. They also have strong ties with the industry. If I remember correctly, they signed an MoU so that their Pure Mech degree is recognized by MIT.
*
I'm not into Mechanical Engineering , I'm more geared towards Physics at the moment . This might change , that's why I'm keeping my options open , planning to do A Levels first ( which means IPTA would be out of the picture for me ) , and I've to really dig deep for scholarships after A Levels .
v1n0d
post Dec 15 2013, 09:39 PM

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QUOTE(maximR @ Dec 15 2013, 09:35 PM)
I'm not into Mechanical Engineering , I'm more geared towards Physics at the moment . This might change , that's why I'm keeping my options open , planning to do A Levels first ( which means IPTA would be out of the picture for me ) , and I've to really dig deep for scholarships after A Levels .
*
When it comes to Physics, my heart is with UM. I spent a couple of days there in the IPO selection camp, it still ranks as one of my top 3 academic experiences.
Krevaki
post Dec 15 2013, 10:02 PM

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QUOTE(maximR @ Dec 15 2013, 09:27 PM)
Done with SPM . Starting on more 'advanced' concepts for now to get used to them before PreU . How are the lecturers at  USM by the way ? How 'rigorous' is the curriculum for Mech Eng ?
*
shocking.gif I have a secret admirer.

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Jokes aside, that is good to know. How were the papers this year? Any "special" things?

The lecturers are okay, I guess. But then I have never walked into lectures by lecturers at other universities, unless you count MIT OCW in. The curriculum, by my estimate, would be slightly above the average IPTA standards. There are some courses that are more intense than others, and then there are those that nobody cares about. And let me tell you one fact about engineering: we are very software intensive. So far I've been exposed to 7 different softwares, and there are more to come.

By the way, USM accepts A-levels, AUSMAT, SAM and such, other than the usual ones, so IPTA is not entirely out of your reach. (This bit of info may be outdated, so don't quote me on this.)
maximR
post Dec 15 2013, 10:03 PM

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QUOTE(v1n0d @ Dec 15 2013, 09:39 PM)
When it comes to Physics, my heart is with UM. I spent a couple of days there in the IPO selection camp, it still ranks as one of my top 3 academic experiences.
*
Do you know how I can be involved with the camp ? I've heard of the IMO one but information about IPO is scarce . sad.gif

How do you think I should prepare for it ? IPO involves a lot of college level Physics , not sure if I can manage to self-study everything .
maximR
post Dec 15 2013, 10:09 PM

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QUOTE(Krevaki @ Dec 15 2013, 10:02 PM)
shocking.gif I have a secret admirer.

» Click to show Spoiler - click again to hide... «


Jokes aside, that is good to know. How were the papers this year? Any "special" things?

The lecturers are okay, I guess. But then I have never walked into lectures by lecturers at other universities, unless you count MIT OCW in. The curriculum, by my estimate, would be slightly above the average IPTA standards. There are some courses that are more intense than others, and then there are those that nobody cares about. And let me tell you one fact about engineering: we are very software intensive. So far I've been exposed to 7 different softwares, and there are more to come.

By the way, USM accepts A-levels, AUSMAT, SAM and such, other than the usual ones, so IPTA is not entirely out of your reach. (This bit of info may be outdated, so don't quote me on this.)
*
I remember you asking about USM , so yeah , that's how I got to know which course and where you're studying .

Yes . A lot . If you've followed the SPM Thread , you will see a lot of rants . The biggest one is Moral , where LPM had to come up with an official reply for many angry parents/students . The sudden change in format , where 'nilai' is no longer needed in essay questions , and 80% comprises of KBKK questions . Sejarah was like this too .

I see . I'm still a little bit undecided . I mean I still have a passion for Physics , but interests change , so I'm trying to be exposed to as many things as possible . I'm reading up on Logic , does engineering involve stuff like Mathematical proofs , number theory , etc or does it require only calculus ?
v1n0d
post Dec 15 2013, 10:10 PM

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QUOTE(maximR @ Dec 15 2013, 10:03 PM)
Do you know how I can be involved with the camp ? I've heard of the IMO one but information about IPO is scarce . sad.gif

How do you think I should prepare for it ? IPO involves a lot of college level Physics , not sure if I can manage to self-study everything .
*
Honestly, I have no idea. My F6 physics teacher picked my buddy and I to take the statewide exam and we scored. Next thing you know, we were part of 40-student pool for national team selections.

Most of the material covered in the selection camp was college level, so we were pretty lost. I do remember an experiment were asked to approximate the value of g without using a stopwatch.

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