# Math Challenged.

Started by February 24, 2018
```I know I am losing it, but I want to bring it back.

I have screwed up some things. Figuring out a roll of wire, I had 95 turns of about
12" diameter. I thought pi was times radius, and that is because of not using it.
And then I thought there was 1,700+ feet in a box that came with 1,000 feet. I had
forgotten to divide by 12 to get feet out of inches.

Losing it. Someone just commented on that in SED. Well I want it back.

A recent gaff was about an OP AMP circuit. Had a 10 K resistor from output to the -
input. There were other 10 K resistors that fed it. At the beginning it completely
escaped me that it iis feeding a null point and there is no current. I should have
known that offhand.

But math is a bi challenge to me. I understand some. Interpolating variables like
12=4X3 and 12/3=4 and all that. I can also handle the 3a and 4b stuff. When they got
to polynumials in school the lost me.

And now things seem to have changed. I never heard o tau before recently, apparently
it represents a change in some variable. I thought delta did that. So, what is the
difference ? i have not gotten an answer I can understand anywhere.

I finally figured out something about the input impedance of a common emitter amp
stage. If the collector is tied right to the supply it is Re times hfe. I thought
when there is resistance to the collector that this would change, but now I  think
it doesn't. Looking at the curves of collector current it seems stable with voltage
changes. That means it has no effect and under normal condition like no clipping
etc. so it is still at least close to Re times hfe.

If someone wants to help I am all ears. Because of my eyesight it is difficult to
read and upgrade my skill set. I am hoping they can fix that and I have no shame
taking medicaid because I DID pay taxes for many years and I really cannot work
now.I fix stuff in the basement but not fast enough to charge by the hour.

So really, in this thread I intend to pose questions and hopefully get good answers.
If you have the extra time of course.

The first thing is what the hell is tau exactly ?
```
```In article <7869e906-cdc3-4149-aea5-37f27788911d@googlegroups.com>,
jurb6006@gmail.com says...
>
> If someone wants to help I am all ears. Because of my eyesight it is difficult to
read and upgrade my skill set. I am hoping they can fix that and I have no shame
taking medicaid because I DID pay taxes for many years and I really cannot work
now.I fix stuff in the basement but not fast enough to charge by the hour.
>
> So really, in this thread I intend to pose questions and hopefully get good
answers. If you have the extra time of course.
>
> The first thing is what the hell is tau exactly ?
>
>

Tau is 2 time pi or about 6.28 as pi is about 3.14.

You need to learn how to Google for simple things like this.

For a better explination.

http://math.wikia.com/wiki/Tau_(constant)

```
```>"Tau is 2 time pi or about 6.28 as pi is about 3.14. "

Wow, thanks. Now I see how I so misunderstood my math tutor. And the wire thing, if
I use radius instead of diameter then it is tau, why was that so damn hard to pick
up ?

My math tutor is very advanced and I find him nearly impossible to follow. I am his
electronics tutor and he probably finds me the same. Granted I am only half there,
but he is still in the basics and I can handle that. In math, he goes too far too
fast. Maybe I am slow...

Thanks for the answer. I will think up more questions. Don't get floored by them.
```
```On 24/02/2018 23:52, jurb6006@gmail.com wrote:

> And now things seem to have changed. I never heard o tau before
> recently, apparently it represents a change in some variable. I
> thought delta did that.

You are correct; delta is often used in math and physics to represent a
change in a variable, such as the gradient of a straight line graph
would be Delta Y / Delta X

>
> The first thing is what the hell is tau exactly ?
>

It depends.  Tau is often used in engineering to represent a time
constant, for example:

https://en.wikipedia.org/wiki/Time_constant

There are however many other uses in math and physics, for example see:

http://mathworld.wolfram.com/Tau.html

https://en.wikipedia.org/wiki/Tau#Mathematics

```
```On Sat, 24 Feb 2018 23:45:14 -0500, Ralph Mowery wrote:

> jurb6006@gmail.com says...
>>

>> The first thing is what the hell is tau exactly ?
>>
>>
>>
> Tau is 2 time pi or about 6.28 as pi is about 3.14.

We more commonly encounter Omega, which is 2*pi*the frequency of
interest. It's represented by a funny looking 'w'.

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```
```jurb...@gmail.com wrote:

-------------------------
>
> >"Tau is 2 time pi or about 6.28 as pi is about 3.14. "
>
> Wow, thanks. Now I see how I so misunderstood my math tutor.
> And the wire thing, if I use radius instead of diameter then
> it is tau, why was that so damn hard to pick up ?
>
> My math tutor is very advanced and I find him nearly impossible to follow.
>
>

** Sounds like a bit of a jerk too, tau meaning " 2pi " is NOT accepted in math and
likely never will be.

Good old " pi" is all you need to know about !!

Giving double the famous ratio a new name ( one already used for other jobs mind you
) and dropping the centuries old one is ABSURD.

FYI:

A close approximation to " pi " is the ratio 22:7 = 3.1428...

A close approximation to "square root 2" is 99/70 = 1.41428...

...  Phil

```
```On Sat, 24 Feb 2018 15:52:35 -0800 (PST), jurb6006@gmail.com wrote:

>I know I am losing it, but I want to bring it back.
>
>I have screwed up some things. Figuring out a roll of wire, I had 95 turns of about
12" diameter. I thought pi was times radius, and that is because of not using it.
And then I thought there was 1,700+ feet in a box that came with 1,000 feet. I had
forgotten to divide by 12 to get feet out of inches.
>
>Losing it. Someone just commented on that in SED. Well I want it back.
>
>A recent gaff was about an OP AMP circuit. Had a 10 K resistor from output to the -
input. There were other 10 K resistors that fed it. At the beginning it completely
escaped me that it iis feeding a null point and there is no current. I should have
known that offhand.
>
>But math is a bi challenge to me. I understand some. Interpolating variables like
12=4X3 and 12/3=4 and all that. I can also handle the 3a and 4b stuff. When they got
to polynumials in school the lost me.
>
>And now things seem to have changed. I never heard o tau before recently,
apparently it represents a change in some variable. I thought delta did that. So,
what is the difference ? i have not gotten an answer I can understand anywhere.
>
>I finally figured out something about the input impedance of a common emitter amp
stage. If the collector is tied right to the supply it is Re times hfe. I thought
when there is resistance to the collector that this would change, but now I  think
it doesn't. Looking at the curves of collector current it seems stable with voltage
changes. That means it has no effect and under normal condition like no clipping
etc. so it is still at least close to Re times hfe.
>
>If someone wants to help I am all ears. Because of my eyesight it is difficult to
read and upgrade my skill set. I am hoping they can fix that and I have no shame
taking medicaid because I DID pay taxes for many years and I really cannot work
now.I fix stuff in the basement but not fast enough to charge by the hour.
>
>So really, in this thread I intend to pose questions and hopefully get good
answers. If you have the extra time of course.
>
>The first thing is what the hell is tau exactly ?

They invented TAU to avoid the letter Pi.
It is a Greek letter, pronounced "Pe" in English mumble.

Because the Muricans and Britts cannot pronounce anything correctly.

They say "pie" stealing a piece from Grandmother's apple-pie.

https://www.bettycrocker.com/recipes/scrumptious-apple-pie/

Trying to speak like a human, they inadvertently say "pee",
feeling wet between their legs.

That's the whole TAU story.

w.
```
```On Mon, 26 Feb 2018 08:17:09 +0100, Helmut Wabnig wrote:

>
> Because the Muricans and Britts cannot pronounce anything correctly.

Many Germans can't speak properly either. East of the Elbe and it's all
impenetrable 'dunkeldeutsch' IME.

--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
```
```>"We more commonly encounter Omega, which is 2*pi*the frequency of
interest. It's represented by a funny looking 'w'. "

I seem to remember that is the lower case omega, as opposed to the upper case
meaning Ohms.
```
```>"** Sounds like a bit of a jerk too, tau meaning " 2pi " is NOT accepted in math
and likely never will be. "

No no no, he is not the one who said it was 2 Pi. But he somehow intended to use it
for the pulleys, but I am not sure for what.

>"Giving double the famous ratio a new name ( one already used for other jobs mind
you ) and dropping the centuries old one is ABSURD. "

Radius is used in geometric formulae other than figuring circumference. It is used
in the calculation of sin/cosine and a bunch of other things. I was reading up on it
but gave it up because trig tables are a dime a dozen. Like the impedance nomograph
someone posted. I saved it and haven't done the 2 pi F C thing for some time now.

It is easy enough to write 3.1416, as near as I calculated years ago IIRC was
3.14159265135 and I am not sure about the last digit. I think 5 was a guess, but
that is pretty accurate. (if it is that is)

```