Math Is Fun Forum

  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

Pages: 1

#1 Re: This is Cool » 2006 Ig Nobel Awards » 2006-10-09 22:14:54

ant

lol he used to work with my dad, and he's very prominent at the uni, and in aus in general.
the results of his research on this topic can be found at
http://www.abc.net.au/science/k2/lint/default.htm
and in more detail at
http://www.abc.net.au/science/k2/lint/results.htm

#2 Re: This is Cool » 2006 Ig Nobel Awards » 2006-10-06 02:11:31

ant

the link wasnt working, but wiki has lots on the subject... my favs are

Chemistry, 1993 - Presented jointly to James Campbell and Gaines Campbell of Lookout Mountain, Tennessee, dedicated deliverers of fragrance, for inventing scent strips, the odious method by which perfume is applied to magazine pages.

how did we manage without these guys?

Mathematics, 1993 - Presented to Robert W Faid of Greenville, South Carolina, farsighted and faithful seer of statistics, for calculating the exact odds (710,609,175,188,282,000 to 1) that Mikhail Gorbachev is the Antichrist.

im glad that's sorted out.

Astrophysics, 2001 - Presented to Dr. Jack Van Impe and Rexella Van Impe of Jack Van Impe Ministries, Rochester Hills, Michigan, for their discovery that black holes fulfill all the technical requirements for the location of Hell.

well these guys won't be heading there, so they don't have to worry anyway

Interdisciplinary Research, 2002 - Presented to Karl Kruszelnicki of The University of Sydney, for performing a comprehensive survey of human belly button fluff -- who gets it, when, what color, and how much.

ive actually met this guy a few times... interesting work too!


it's all quite hilarious.

#3 Re: Help Me ! » absolute value inequality » 2006-10-06 01:48:31

ant

thanks for all the help!
i think im getting it... i get where i went wrong at first (also, in one of the lines, i put all the inequality signs the wrong way round, which wasn't helpful. *remembers that crocodiles always eat the bigger fish*)

so just to reiterate, can you just ignore the part that says  -3 ≤ x² ?

i also graphed it, just to check!

thanks for all the help!

index.php?act=Attach&type=post&id=1248


nup. i cant figure out how to post a pic. no probs tho. thanks again tongue

#4 Re: Help Me ! » absolute value inequality » 2006-10-04 18:28:56

ant

ok i might have just answered my own question, but could someone please check?

can you do something by saying

l x² - 1 l = 4

x² - 1 = +/- 4

then

x² - 1 = - 4
x² = -3                 so NO SOLUTION

and on the other side:

x² - 1 = +4
x² = 5

x = =/-√5

and then cos it wasnt equal to, it was less than or equal to, you then say

-√5 ≥ x ≥ √5

or you could graph it to check this.

does this work?

#5 Re: Help Me ! » Slope of a line » 2006-10-04 18:19:33

ant

the best thing to do is draw a diagram and put everything in the same units ...
|\
| \
|   \
|     \
|       \
|1       \
|8         \
|0           \
|0             \
|                \
|<-17160ft->\ TOM

then slope is found by dividing the 'rise' (vertical movement - 1800ft) by the 'run' (horizontal movement - 17160ft)

so you get slope = 1800 / 17160
= 0.104895.....
= 0.10 (to the nearest hundredth)

could someone please check all that tho?

#6 Help Me ! » absolute value inequality » 2006-10-04 18:01:19

ant
Replies: 8

Hi im having a bit of trouble with an absolute value inequality...


l x² - 1 l ≤ 4


i know that sounds dumb, but because of the squared? i'm rather confused...the answer reckons its    -√5 ≥ x ≥ √5
but i just don't agree. when you solve don't you get -3 on the left?
and then what do you do about the fact that you can't take the root of a negative number? i'm not sure what to do after

-4 ≤ (x² - 1) ≤ 4

-3 ≤ x² ≤ 5

thanks a bunch!!!!

#7 Help Me ! » Going crazy over simple question » 2006-08-02 00:12:47

ant
Replies: 1

Ive got this question and the parts make sense but it doesnt work when i put it together. im not sure if that made sense, so ill just go straight to the question...

Prove:

1 - cos2x   
---------  =  tan²x
1 + cos2x

So i can do this part, using different expansions of cos2x

Then it says

Use this to prove that   tan π/8  = √2  -1
If you put this in a calculator it's true, and we just proved that the other two expressions were equal.
But when i sub in π/8 for x in the cos expression, i get 2 - 2√2  -1 , which is definately not equal to √2  -1.

so i dont know what im doing wrong, cos it seems so simple, but it's not working!dizzy

can anyone help?

#8 Re: Help Me ! » mathematical induction qu » 2006-06-07 18:14:27

ant

hey thanks that's really helpful - i couldnt get the step with the expansion.
at the end, could i then say

if
5^k > k^5/5 + k^4 + 2k^3 + 2k^2 + K + 1/5
then
5^k > k^5/5
and also
5^k > k^5

is that logic ok?

#9 Help Me ! » mathematical induction qu » 2006-06-07 01:17:36

ant
Replies: 3

Hey guys there’s this inequalities mathematical induction question which I absolutely cannot do. Could someone please give it a go cos there aren’t any answers in the book. I’ve tried everything I can think of, even expanding (k+1)^5  but I still can’t get it, even tho I can see that it’s true just from common sense.

[^ = raised to the power of]

Prove:

5^n ≥ n^5        when k ≥ 5

thanks smile

Pages: 1

Board footer

Powered by FluxBB