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#3477 Re: Help Me ! » Find a formula for a recursion by induction » 2005-09-27 07:46:07

I don't see what your asking.  Something seems jumbled.
All I see is that your example keeps increasing by an amount that goes up by one each time.

#3478 Re: Help Me ! » poly-angles » 2005-09-27 07:36:31

The fractional values of n between whole numbers are totally meaningless.
Is the 36 degree figure mentioned, is it a ten sided figure?  Why do you measure that angle, and not the
one you can actually see?  180 - 36 degrees.  Probably because 36 times 10 is 360.

V = 360 / n, for n integers > 1. (or 2 if you want to start with a triangle)

Or maybe the hint is that the 36 degree angle is the angle in the point of a
five pointed star?  If that is the case, then

V = 180 - (360 / n)

#3479 Re: Help Me ! » Tough calculus question help needed badly. » 2005-09-27 06:37:12

I don't know how to do proofs, but aren't these just logical truths based on the
definition of Least Upper Bound I just found on the internet as:

The least upper bound, called the supremum, of a set S, is defined as a quantity M such that no member of the set exceeds M, but if ε is any positive quantity, however small, there is a member that exceeds M - ε.

The least upper bound of a function, f, is defined as a quantity M such that f(x) ≤ M for all x in its domain, but if ε is any positive quantity, however small, there is an x in the domain such that f(x) exceeds M - ε.

#3480 Re: This is Cool » Einstein's Riddle » 2005-09-27 06:24:23

Took me half an hour.  Pretty fun!

#3481 Re: Help Me ! » Help please » 2005-09-27 05:10:46

The -2 stays on the top (numerator).
The -2^-3 goes to the top as -2^3.
So now you have -2 times -2^3.
Then -2^3 is -8 because -2 times -2 times -2 is -8.
So that times -2 is 16.  So add 16 in the middle term of your
entire problem.

#3482 Help Me ! » cosine of 22 degrees to 200 digits » 2005-09-27 02:52:28

John E. Franklin
Replies: 2

I am computing the cosine of 22 degrees as this:

  0.
  92718 38545 66787 40080 64744 51136 95694 20976 21719 84899
  76151 43020 91240 95628 53406 63474 24128 49358 03932 63935
  15955 64794 31227 33917 40679 02053 01582 30590 07802 06902
  88050 77241 60133 11039 14004 74347 41407 68422 11601 07859

Can anyone check this for me somehow?  Thanks a lot. smile

#3483 Re: Help Me ! » geometry problem: how to determine area » 2005-09-23 12:42:27

squareinsquare.jpg

line2: y=2x

line1: y = -x/2  + a

line3: y=2x - a

intersection lines 1 and 2 is (0.4a,0.8a)

intersection lines 1 and 3 is (0.8a,0.6a)

small square side length is square root of ((.4² + .2²)a²), which is the square root of 0.2a².

If you square the side length for the area, you get 0.2a²,
which is five times smaller than the big square's area: a².

#3484 Re: Help Me ! » I Need Help With A Home Work!plz » 2005-09-17 11:56:48

Do you have to consider rotating each piece the 4 ways it can rotate?  or maybe only for the center ones?
Maybe not?

#3486 Re: Help Me ! » Polynomials » 2005-09-15 10:48:47

7x - 2(x - 3) = 9x - 5
7x - 2x + 6 = 9x - 5
5x + 6 = 9x - 5
11 = 4x

#3487 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 10:07:16

I think you missed my previous post that noted that 4.45 can round up to 5 when 5's round upward and the rounding
occurs more than once in a sequence on a particular data point.
This makes the exact opposite argument you made prior about rounding down being biased. 
So rounding up is biased because 56% of data rounds upward and 44% of data rounds down.

But rounding down is biased because 55% of data rounds downward and 45% rounds upward.
Did you catch the joke here with the numbers I used for percentages.
For 56-44, I rounded up, but for 55-45, I rounded down! smile

#3488 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 08:58:38

You asked what I meant by the following:
Also 0 + 1 + 2 + 3 + 4 is not equal to (10-5) + (10-6) + (10-7) + (10-8) + (10-9).  (Your method of rounding 5's up)
However 1 + 2 + 3 + 4 is equal to (10-6) + (10-7) + (10-8) + (10-9).  (My method of doing nothing with 5's)

What I meant above is that if you round off the one's place to the ten's place, then the amount you are
rounding can be -4 to +5.  (This is not as good as -4 to +4 or -5 to +5, which has symmetry.)
The 0 + 1 + 2 + 3 + 4 are the amounts you could round down and the
(10-5) + (10-6) + (10-7) + (10-8) + (10-9) are the amounts you would round up if
5's round up.

(Off the subject, I came up with a number system explained in  "This is cool." section about a base-10 number
system where the digits go from -4 to +5, and I never liked the fact that it was not perfectly symmetrical.)
In an odd base number system, I think you can be symmetrical.  For example, base-3 could go from
-1 to +1, or base-9 could go from -4 to +4.)

#3489 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 08:37:10

The tables turn again!
Your dumb method this time (5's round up):
4.445
4.45
4.5
5.
My good method this time (5's round down):
4.445
4.44
4.4
4.
So now we have seen that both methods, going up or down are flawed!
So now we can argue there is no good rounding method known to man yet. smile

#3490 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 06:15:45

Hey, I think I'm finally coming around to your line of thinking!
Your method (5's round up)
5.555
5.56
5.6
6.

One of my dumb methods (5's round down):
5.555
5.55
5.5
5.

I guess my symmetry principle fails somewhere...

#3491 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 05:29:41

I believe 9.50000000000000000001 should be rounded to 10.
I believe 9.49999999999999999999 should be rounded to 9.
I hope we can agree on this at least.

#3492 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 05:15:48

You're right, my mistake.  I just drew a number line with arrows and dots at the 1/2 marks, and you're correct.
I didn't know which way was which, so for me, the odds got the advantage, but now I see what you mean!
This is very interesting.
But I would like to pose a new algorithm for some problems.  Simply toggle back and forth on each
successive rounding that needs to be done that is exactly .5.  Go up once, down the next time.
How do you like that?   No matter what we do it's not perfect though.

#3493 Re: Help Me ! » Rounding .5 up or down? » 2005-09-15 04:44:41

I have a hunch that your example of what statiticians do is incorrect.
If the input # is even in the place value we are keeping, then we go one way, and
if odd, then the other way, but that's just my guess.

Also 0 + 1 + 2 + 3 + 4 is not equal to (10-5) + (10-6) + (10-7) + (10-8) + (10-9).  (Your method)
However 1 + 2 + 3 + 4 is equal to (10-6) + (10-7) + (10-8) + (10-9).  (My method)

#3494 Re: Help Me ! » Difficult Matrix Math Problem » 2005-09-15 04:36:14

In mR above, why are the 159#'s not all the same?  They end in 0, 3, or 5?
I thought the three 3.14 numbers might make this more symmetrical, but I don't know anything yet.

#3495 Re: Help Me ! » Difficult Matrix Math Problem » 2005-09-15 03:09:47

Thanks for explaining in more detail, however, I must admit that my knowledge
of matrices is far too limited at this point to even get a basic understanding of
what is going on.   I am pretty good with trig, however, and wondered if the
...97... number could be computed with trigonometry.

#3496 Re: Help Me ! » Rounding .5 up or down? » 2005-09-14 19:25:12

And if you are in an odd base number system, like base-3, then you have a
new kind of viewpoint.
1 rounds down.  2 rounds up.   0.111111111111 repeating is 1/2
0.1 is 1/3   0.2 is 2/3's    0.12 is 5/9ths.

#3497 Re: Help Me ! » extreem of function » 2005-09-14 19:02:17

I'm very interested in knowing what c stands for?

#3498 Re: Help Me ! » Set Theory Problem » 2005-09-14 18:59:30

Well for starters, I see it is true for this example:
n=3 and r =2
sets are {1,2}, {1,3}, and {2,3}. 
So average of smaller in each pair is (1 + 1 + 2)/3
I'll try more later...

#3499 Re: Help Me ! » Rounding .5 up or down? » 2005-09-14 18:28:12

In your 50 possibilities, the problem is that the sum of the distances you are rounding up is
greater than the sum of distances you are rounding down. 
How it really goes is:   .00 doesn't round anywhere; the value stays the same.
                                 .50 rounds up or down, so it's a don't care.
                               49 cases of .01 to .49 round down the same amount as 49 cases of .51 to .99 round up.

#3500 Re: Help Me ! » Difficult Matrix Math Problem » 2005-09-14 18:22:00

Can you explain how you get the ...97... numbers in mR?

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