# Understanding Electronics Basics #2

Discussion in 'General Electronics Chat' started by cowboybob, Mar 26, 2012.

1. ### Muttley600New Member

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I've gotta get my math sorted, cause your showing me * & calling it division????
This is another 'oh my god, you can't short a live wire out moment'
I'll nail it tomorrow & we can go forwards

Thanks for sim CBB, will have a play

On the morrow guys, gotta catch up on sleep then get back to this after work

2. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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The first 1000 prime numbers are:

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997...

When you factor, you try to get as many of these (prime numbers, they go on forever) to divide evenly into the number.

So for 16. It's even, so it's divisible by 2. and you get 2*8

8 is even so it;s divisible by 2, so you get 2* (2 * 4)

4 is even, so it's divisible by 2.

So you get 16 = 2* 2 *2 * 2

3. ### Muttley600New Member

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ok, that took a while & I still might have it wrong, are you saying you keep breaking a number down until only prime numbers fit into it

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5. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Yep, That's called "prime factorization".

You can "factor" any which way you like though. e.g. 100 = 10 *10 = 50*2.
You can say that 2, 10, 20, 50 and 5 are "factors" of 100.
That just means that the "factors" divide evenly.

Both concepts are useful. In algebra, there is a lot of "Find the two factors of X which when added or subtracted equal Y.

So we have:
Factors - numbers that divide evenly into the number x
Factoring - numbers that multiplied together equal the number x
Prime Factoring - primes multiplied together equal the number x

Last edited: Apr 3, 2012
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6. ### Muttley600New Member

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I've deleted the ones I understand but what are these, they don't make sense

7. ### Muttley600New Member

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Your going to be very sad that I don't know why you've taught me that because I still don't see the logic or need behind it, what are you showing me & why

8. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Remember the √192? and you could not get their answer of something like 8√3 or something like that?
---
Ok, the √8 = 2√2; 8 factored is 2*2*2, so you can take out a pair of 2's from under the √symbol as a 2; so you get 2√2.
11 and 13 are prime so there is nothing to take out.
√10 = sqrt(2 * 5) and there isn't a pair of anything to take out.
√14 =√2√7. I threw that one in to throw you. You can't take out a pair, but you can take out each of the terms as a √. This isn;t something you would normally do.

9. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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If we were dealing with cube roots, factoring 27 would give 3 * 3 * 3 and thus the cube root of 27 is 3.

10. ### Muttley600New Member

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I think we are at it again, remember how I wondered what hit me when you put formulas up, I learnt a bit of algebra & grasped enough basic to get me through, while we've hit the runway half way along again (sorry been on phone sorting help for work)
I somehow need to be able to relate to this, what does it come under so I can look it up & try to understand it a bit better?

11. ### Muttley600New Member

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ok, lets try working on this, show me the formula for this, I can see numbers work but if I'm guessing correct your gonna put a divide somewhere in formula thats going to throw me & can you do this on calculator?

12. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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You can if you have a button that can take the nth root of a number. There is usually a super scripted n before the √ symbol.

If you can take LOGs in base 10, you can also do it.
Log10(27) = 1.431363764
Divided by 3 = 0.477121255
10^ 0.477121255 = 3

Oops, too complicated,

anyway
Factoring 27
You get 3 * 9
and then 3 * 3 * 3
Cube roots just require 3 numbers to be multipled together, so the answer is 3.'

We can do the cube root of 100 the same way and get: 4.641588834 so 4.641588834
*4.641588834*4.641588834 = 100

13. ### Muttley600New Member

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Lol, I knew it, you simply divide the answer, but I still need to relate better to that square root symbol, let me have another look
& what is that thing that looks like a house roof that keeps appearing?

14. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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The house roof or carrot is this symbol "^". It denotes exponentiation in computer land.

In Math land it's

thus x^n is equivalent to

The cube root of x is denoted by

Last edited: Apr 3, 2012
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15. ### Muttley600New Member

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See, I look at that & can instantly relate to it
Yes, I can hear that sigh of relief

16. ### Muttley600New Member

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ok, (so first one is) 256 - 64 = (second) 192 (third) 4*4*4 (64) *3

I'm not giving up if I have to do this 100 times until I remember it, don't panic, got it for the second time, I shall promise not to ask how to solve this until thursday at the earliest now

so we basically are working out the cube, taking one side then cubing that

we're not even doing that, relating back, we are just cubing bottom measurement, why didn't you say that

Now before we go any further, I need to carry on learning special triangles so I can put names of sine/cosine etc to them, we have movement I'll get there in the end

Last edited: Apr 3, 2012
17. ### Muttley600New Member

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Damn, you'd given me the answer, I just didn't see it at the time, sorry for doubting

18. ### Muttley600New Member

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just double checking
8 cubed * 3 = 192

So other triangle shown on post #45

5 squiggle 3 would be 5 cubed * 3 = 75

is that right? not that I don't trust myself or anything

Last edited: Apr 3, 2012
19. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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No. 8 √3 = √192 ~= 13.85640646 No cubic anything.

5√3 would be 5 * 1.732050808 ~= 8.660254038

The ~= means approximately equal to.

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20. ### Muttley600New Member

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ok, slightly misunderstood, so:
5 cubed * 3 = 75 so if I change it to mean sqrt of 75 = 8.660254038

now I see it

Last edited: Apr 3, 2012
21. ### KeepItSimpleStupidWell-Known MemberMost Helpful Member

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Huh? 5 cubed = 5 * 5 * 5 = 125;

multiplied by 3 = 375

75 factored is 5 * 5 * 3
If you wanted to take √75 exactly, you would end up with 5√3 or your 8.66 number

Last edited: Apr 3, 2012