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#1 Re: Help Me ! » Degrees of Freedom » 2012-06-23 07:56:17

Yes, thats what I'm doing. big_smile Sorry

#2 Help Me ! » Degrees of Freedom » 2012-06-23 07:36:37

Replies: 3

Statistics this time.

I have a poisson distribution, and I am just trying to work out my degrees of freedom.

I have 7 columns of data. I have the mean. I have not worked out the variance yet. But I do have the total frequency.

So does the total expected frequency count as a constraint

In other words, is my degree of freedom 7-1=6 or 7-2=5

(it does make a difference because 7-1 means that it is a poisson distribution and 7-2 means it isn't)

#3 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 03:19:45


(Just so you know, I am acknowledging this website in my log for all the help you guys have been giving me. My teacher said I can get all the help I need as long as I acknowledge it.)

#4 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 03:14:40

That thanks a million was to you both

(Sorry Stefy if that wasn't obvious).

You are both absolute stars

#6 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 02:51:35

So your answer, bobby, that is the minimum? That is the answer?

#7 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 02:45:18

So then l-x=l-[4l/(pi+4)]
= L*Pi/(pi+4)

Is that the answer? That's the minimum right? How do I find the max? I imagine it is just using the whole length of rope for a circle, but how to I prove that? I can prove that a circle and a square of a set perimeter, the circle will have the biggest area.

#8 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 02:25:34

Can you just explain what you did please?

I'm guessing that we divide through by x to get it on its own.

#9 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 02:11:09

Hey bobbym. Please see post above. How do I solve it equated to 0?

#10 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 01:57:59

Right so I have got

So the df/dx is

Pray tell what do I do now?

(I know I have to equate it to mean 0, but what do I actually have to do?)

#11 Re: Help Me ! » Minimising area of square and circle » 2012-06-23 00:13:40

thanks. I obviously need to add x^2/16 to the end result you have there (I am guessing) and so do I do the cross multiplying?

Also, how do you so all that maths set up on the forum?

#12 Re: Help Me ! » Minimising area of square and circle » 2012-06-22 23:54:29

Thanks anon.

Sorry, I've got the deadlines looming and I've burnt myself out

#13 Re: Help Me ! » Minimising area of square and circle » 2012-06-22 23:46:52

Okay, what's the correct way to square it.

#15 Re: Help Me ! » Minimising area of square and circle » 2012-06-22 23:36:21

How do I do that. Do I first need to get rid of the brackets? So it would be


Then where do I go? Can we take it a step at a time please?

#16 Help Me ! » Minimising area of square and circle » 2012-06-22 23:20:57

Replies: 29

A piece of string of length L is to be cut into two pieces. One piece is formed into a square, the other into a circle.
a)Where, if anywhere, would the string be cut to that the total area of the two shapes is a small as possible
Where, if anywhere, should the string be cut so the area is as large as possible

This is what I have:


I'm assuming that the maximum would be just a circle, but I don't know how I'd show that. And not sure how I'd do the minimum

#18 Re: Help Me ! » Harder Substitution » 2012-06-04 07:32:21

It's okay, my real name isn't amberzak.

What was the method you used bob? And thanks, you have been very helpful

The link you gave me doesn't work sad

#19 Re: Help Me ! » Harder Substitution » 2012-06-04 05:17:35

Anon, I have not yet. How would I do that?
Bob, I am guessing it's still answer in process. I get so far and then couldn't get further. I think the sec^3 theta tan theta is a hint.

#20 Help Me ! » Harder Substitution » 2012-06-03 22:36:53

Replies: 19

By using the Substitution u=cot theta or otherwise, find the integral of cot ^4 theta d theta

My teacher says there is a really simple way to do this, so it shouldn't take hours.

He also gave us a hint of writing down sec^3 theta and tan theta, but I can't see how we can get to that.

Any ideas?

#21 Help Me ! » Calculus - Intergration by Substitution » 2012-06-01 20:41:51

Replies: 5


I can't figure this one out.
Let U = lnx

Do I tried to differentiate lnx by du. I got du=1/x dx. Then I know I need dx by itself, but not sure how to get to that.

Can anyone help me?

Thanks all

#22 Re: Help Me ! » Intergrating a function with partial fractions - calculus » 2012-05-17 03:13:52

No, not really. Could you please go through that? I kind of see it.

#23 Re: Help Me ! » Intergrating a function with partial fractions - calculus » 2012-05-16 07:19:28

Okay. so the first thing I need to do is find A and B as shown above?

Then, how do I integrate the fraction. My teacher said it was something to do with Partial Fractions, and did say if i couldn't do the question not to worry because I've not studied partial fractions before, but I would like to at least understand how the answer is derived.

#24 Re: Help Me ! » Intergrating a function with partial fractions - calculus » 2012-05-15 21:17:47

I've never seen the x with the arrow before. What does it mean?

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