More math stuff...

[PurplePoot]

1 = Sqrt(1) = Sqrt((-1)(-1)) = Sqrt(-1)Sqrt(-1) = -1

---

a=b
a^2 = ab
2a^2 = a^2 + ab
2a^2 - 2ab = a^2 - ab
2(a^2-ab) = 1(a^2-ab)
2 = 1

---

Disprove 'em (the formulae, not the results), +rep for the first one who shows why both are incorrect. (That means if you only get one, someone else can steal it)

Oh, and we can spam more math nerdiness here once these questions are answered.

And please don't cheat, it takes the fun away from it.

 

[LordOglog]

1 = Sqrt(1) = Sqrt((-1)(-1)) = Sqrt(-1)Sqrt(-1) = -1

because Sqrt(-1)Sqrt(-1) doesn't equal -1.

 

[Mechanical Man]

I proved this way (De Moivre): z^n=r^n*(cos(fi/n)+i*sin(fi/n))

Polar coordinates:
-1+0i=(-1)*(cos(pi)+sin(pi))
1+0i=(-1)*(cos(0)+sin(0))

sqrt((-1)(-1))=sqrt(1)=1*(cos(0)+i*sin(0))=1*(1+0i)=1

sqrt(-1)sqrt(-1)=sqrt(-1)*(cos(pi)+i*sin(pi))*sqrt(-1)*(cos(pi)+i*sin(pi))=i*(1+0i)*i*(1+0i)=i*i=-1

Evidently the function sqrt(n) is not linear.

The second one is just an illegal division with 0. Now you can spam more math nerdiness. What do you mean by cheating?

 

[PurplePoot]

By cheating I mean you can probably google it, in fact I'm almost definitely sure you can with the internet these days...

Anyhow, Sqrt(nn) is only equal to Sqrt(n)Sqrt(n) if n>0, so yeah, that ended faster than I expected it would

Hmm... more math nerdiness...

Anyone know the proper pronunciation of "Euler"? (Yes, this relates to math somewhat, as much as it may seem it doesn't)

 

[donut3.5]

Yoo-ler?
Then bah, I knew the first one because you told me.
--donut3.5--

 

[Dr Super Good]

What is wrong with the folowing, if anything.
2 = Sqrt(4) = -2 = Thirdrt(8)

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64A - 64B = £1068.66
-32A + 32B = £534.34

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A weight with mass 821824.9 grams on the moon was trying to be lifted by a machine. Another machine that applied 2.3 times the force of the machine on the moon tried to lift a 0.3134762 ton mass on earth. The machine on the moon applies a upwards force of 1333 newtons. Both weights were placed on the planet surface.

Both weights slowly gained volocity upwards.

---

Hehe I look foward to your answers.

 

[donut3.5]

1.) You can't really use square roots to say that x = -x, which is stated with one of Poot's previous posts.
--donut3.5--

 

[Modo]

Sqrt(4) = 2 or -2. Saying just one isn't a correct answer.

I will have to get back to you on the others. I suck at maths.

 

[donut3.5]

Right, but it doesn't prove that 2 = -2 by doing
2 = SqRt(4) = -2 then applying transitive property.
--donut3.5--

 

[Dr Super Good]

No one saw the simple answer to the first one. . .
(-2)^3 does not equal 8, it is -8

 

[Samuraid]

1 = Sqrt(1) = Sqrt((-1)(-1)) = Sqrt(-1)Sqrt(-1) = -1

Sqrt((-1)(-1)) != Sqrt(-1)Sqrt(-1)
(xy)^1/2 only equals (x^1/2) (y^1/2) when x and y are both positive real numbers. Otherwise the rule fails.

a=b
a^2 = ab
2a^2 = a^2 + ab
2a^2 - 2ab = a^2 - ab
2(a^2-ab) = 1(a^2-ab)
2 = 1

You cannot mathemetically get from here:
2(a^2-ab) = 1(a^2-ab)
To here:
2 = 1

Because, you would be dividing by zero. After all, a^2 = ab, so it really looks like:
2(a^2 - a^2) = 1(a^2 - a^2)
2(0) = 1(0)
which is really:
0 = 0

Q.E.D.

 

[Gilles]

Anyone know how to prove Infinite = 1/4? My teacher told me about it but didn't show me it. I've seen the second one poot posted.

What level of Math are you guys at? I'm in gr.12 math and I don't understand a lot of this.

 

[Modo]

Dr. Super Good, you win. My maths teacher told me that negative numbers to odd powers equal negative numbers but I always forgot.

Gilles, I have Year 12 NSW Australian 2 Unit Mathematics, and I was bad at it. How bad you ask? I failed every test except the HSC, in which I got 54% after scaling ^_^'

 

[LordOglog]

0.999... = 1

0.999...*10 = 9.999...
9.999... - 0.999... = 9 (10 lots of 0.999... - 1 lot of 0.999... = 9 lots of 0.999...)
therefore 9*0.999... = 9
0.999... = 9/9 = 1

 

[The_wand_mirror]

Anyone know how to prove Infinite = 1/4? My teacher told me about it but didn't show me it. I've seen the second one poot posted.

What level of Math are you guys at? I'm in gr.12 math and I don't understand a lot of this.

Prove infinity? i only know this =D

yeah i always get 5.4/10 for tests -.-

 

[Hakeem]

I aced a final once.

 

[HINDYhat]

I'm currently doing g11 math, which is retarded.

 

[Modo]

LordOglog, could you please make your post easier to read. For example:

Proof 0.999... = 1
Let x = 0.999...

The three dots show that it is recurring. Some people put a "9" at the end but I find it unneccesary. You could also just state that all numbers after the decimal are recurring. This should make it easier to read then

0.99999(recurring)*10 = 9.99999(recurring)

There was actually a poll on what people thought of "1= 0.999..."

 

[Jualin]

This type of mathematics is not something they've gotten to at my school. More so the solving of equations we have covered, not the disproving of methods to get at answers by other equations. But since I feel like adding something more than idle breath to this, I'll just tack on a logic puzzle.

Idle breath

A one ton slab of Iridium is sitting in an open area on Earth. There are 2 handles on the slab. How many people would it take to lift the slab assuming that the lifting capacity of each person does not exceed approximately 50 pounds or 25 kilograms. No machinery can be operated or devices like pulleys used.

 

[Gilles]

I'm currently doing g11 math, which is retarded.

I had 94% in math 11, until the final. I didn't study the first half of the year, and almost failed it. I got like 87 or something.

 

[Modo]

A one ton slab of Iridium is sitting in an open area on Earth. There are 2 handles on the slab. How many people would it take to lift the slab assuming that the lifting capacity of each person does not exceed approximately 50 pounds or 25 kilograms. No machinery can be operated or devices like pulleys used.

I forget whether ton is 1000 pounds or 1000 kilograms. I'm pretty sure it is pounds.

My answer would be 1000/50 = 100/5 = 20
So, it would take 20 people to lift the iridium.

When you say that it is a logic puzzle, I don't know where to go from there. I think I am right.

If you want a logic puzzle, I have this:
A man with a backpack is approaching a field. He knows as soon as he gets there, he will die. How is this possible?

 

[Hakeem]

A man with a backpack is approaching a field. He knows as soon as he gets there, he will die. How is this possible?

I don't like riddles that I can see 1000 different correct answers to.

 

[donut3.5]

Modo, its obvious that his backpack is filled with propane tanks and he is approaching a field which is constantly on fire. Everyone knows that one
--donut3.5--

 

[Modo]

I think I may have told the riddle wrong ^_^'

A man with a backpack is approaching a field. He knows as soon as he gets there, he will die. How is this possible?

The answer is he is falling from a plane.

I think this is off-topic though. We should make a new thread for logic puzzles and only discuss mathematics in this one.

 

[donut3.5]

What if in his backpack he has an antigravity device?
Also, I do think a good riddle thread is due.
--donut3.5--

 

[Modo]

I am going to go start one

 

[Mechanical Man]

Poot, where is more math nerdiness?

 

[Modo]

Show how 1+1=1. It is possible, but I do not know how.

 

[PurplePoot]

You people are assuming this is the sort of thing you learn at school.

School is not the only way to learn, you know

Samuraid, good answers, but you didn't get them first.

About my 'Euler' question - it's not pronounced how it looks.

Anyhow, I only post every so often (day or two), don't expect me to spam this hourly or anything

This calls for a math joke.

Two mathematicians were having dinner. One was complaining, "The average person is a mathematical idiot. People cannot do arithmetic properly, cannot balance a check book, cannot figure tips, cannot do percents,..." The other mathematician disagreed, "You're exaggerating. People know all the math they need to know."

Later in the dinner, the complainer went to the men's room. The other mathematician beckoned to the waitress and said, "The next time you come past our table, I am going to stop you and ask you a question. No matter what I say, I want you to answer by saying 'x-squared."

When the other mathematician returned, his companion said, "I am tired of your complaining. I am going to stop the next person who comes by our table and ask him or her an elementary calculus question, and I bet the person can solve it." Soon the waitress came by and he asked, "Excuse me, Miss, but can you tell me what the integral of 2x with respect to x is?" The waitress replied, "x-squared." The mathematician said, "See!" His friend said, "Oh I guess you're right." And the waitress said, "Plus a constant."

---

Kay, here's some more math nerdiness.

Prove Euler's Formula e^(ix) = cos x + i sin x

If you want a hint just ask.

I forget whether ton is 1000 pounds or 1000 kilograms. I'm pretty sure it is pounds.

A Metric Tonne is 1,000 KG.

 

[Eleandor]

Euler = "Oiler" something like that. It's a bit ironic that you're asking to write down how you pronunciate a name...

Oh and as far as I know, 1000 Kg = 1 Ton.

Here's another math joke I heard:

"45" is running away from something... Nobody knows why.
"e^x" meets him and asks what's wrong.
"45" answers: "when turning around the corner, I saw a friggin derivative, and he's going to turn me to nothing!"
"e^x" says: "Oh, don't worry, I'll go fix him, he can't do anything to me, can he!"

And so, e^x walks towards the derivative, and says "stop here, you bastard! you shall no longer bother people when you're on a mathematical killing spree!"
The derivative laughs a bit and says "I'm d/dy".

 

[Kaitech[SanD]]

An old favourite of mine is Which weighs more, a tonne of feathers or a tonne of metal.

 

[PurplePoot]

Hehe Eleandor, you're right there, and maybe it is but maybe it isn't... there's not much other way to communicate such a thing, and it's not that hard to write Oiler

@Kaitech neither... obviously?

 

[Eleandor]

But how do you say "oiler"? The only way to make that clear is to simply write it phonetically, and I'm not going to bother doing that...

(edited earlier post)

 

[HINDYhat]

meh... I know how to prove e^(ix) = cos x + isin x...
but it's a long and boring explanation (and would probably be CnP'd from wikipedia anyway).

 

[LordOglog]

An old favourite of mine is Which weighs more, a tonne of feathers or a tonne of metal.

easy a ton of feathers, because feathers are less compact so when ou try and weigh them you weigh air aswell.

 

[Kaitech[SanD]]

easy a ton of feathers, because feathers are less compact so when ou try and weigh them you weigh air aswell.

Correct!

 

[PurplePoot]

Err, wrong, the weight of the feathers is still a tonne... the weight of the air and the feathers COMBINED is more, but the weight of the feathers is 1 tonne, no more, no less

You should word the question:

If you were to weigh a tonne of feathers and a tonne of metal, which would weigh more?

PS. Please, math, not logic.

meh... I know how to prove e^(ix) = cos x + isin x...
but it's a long and boring explanation (and would probably be CnP'd from wikipedia anyway).

But that's no fun - the interesting part is working it out and doing it yourself. It's much less fun if you already know how, of course, but trying it out and getting it to work the first time is always nice.

 

[Samuraid]

Samuraid, good answers, but you didn't get them first.

I got question #2 first. But you jumped the gun an answered #1. Oh well, it was worth a try.

 

[PurplePoot]

Nah, reply #2 got both right.

 

[Samuraid]

Nah, reply #2 got both right.

Hah, didn't see that either.

* goes to get eyes checked *

 

[GST_Nemisis]

abc as easy as 123....

best maths ever is Ka = (([H+]*[A-]/[HA])

or

Ph = -log((root Ka*c)

 

[Hakeem]

easy a ton of feathers, because feathers are less compact so when ou try and weigh them you weigh air aswell.

The metal is holding water.

I still think it's awesome that cosine is the derivative of sine.

 

[PurplePoot]

I think it's even more awesome that sine is the negative derivative of cosine as well.

 

[Eleandor]

I think people who find sin/cos stuff awesome are nerds...

 

[PurplePoot]

I think you're right. I also don't see how you came to this topic if not expecting such a thing

 

[donut3.5]

I find it odd how (csc^2(x))+(sec^2(x))=(csc^2(x))(cos(x))
Usually adding things doesn't come up to be the same result as multiplying them, besides 2+2 = 2*2
--donut3.5--

 

[Gilles]

Aren't many things in math are like that donut? logX+logY=logXY for example.

 

[donut3.5]

Yeah, but thats inside the parenthesis, not
log(x)log(y)
--donut3.5--

 

[PurplePoot]

Donut, are you sure that 1 = cos(x)/sin^2(x)?

*Thinks about it*

 

[donut3.5]

Whoops, wrote it wrong, should be
(csc^2(x))+(sec^2(x))=(csc^2(x))(sec^2(x))
--donut3.5--