Slide Rules and Logarithms

2009-06-05 05:48:07

#1

Jenspm: penis; +1,716|7156|St. Andrews / Oslo

One of the things I have to cover in my Oral Exam is to use a Slide Rule to prove/shed light on the following task: "Describe the 'arithmical rules' of logarithms, and use them together with the rules of exponentiation to simplify expressions and solve equations and inequalities"

^{sorry if the translation is bad/innacurate}

Now, the actual task is easy enough, but it's the use of the Slide Rule that I haven't completely grasped yet. I've never used it before, and just learned how to via a video on Youtube, lol. So yes, I can multiply, divide, square, cube, root and log, but I can't seem to find the connection. Apparently, it's based on the statement that lg(a) + lg(b) = lg(ab).

So the question I ask of you, BF2s, is: Can anyone shed some light on how the Slide Rule uses logarithms to do calculations (multiplying is my assumption)? Alternatively, any idea how I can use a Slide Rule to prove/show the laws of logarithms?

Thanks for all help/hints/suggestions that may come

https://static.bf2s.com/files/user/26774/flickricon.png

2009-06-05 05:50:06

#2

SamBo:D: Banned; +236|5921|England

Slide rules are basically; one at a time and make sure that its clear at the bottom before you go down.

Last edited by SamBo:D (2009-06-05 07:31:38)

2009-06-05 07:07:42

#3

presidentsheep: Back to the Fuhrer; +208|6385|Places 'n such

http://en.wikipedia.org/wiki/Slide_rule … ponentials

That help?

I'd type my pc specs out all fancy again but teh mods would remove it. Again.

2009-06-05 07:18:30

#4

Jenspm: penis; +1,716|7156|St. Andrews / Oslo

presidentsheep wrote:
http://en.wikipedia.org/wiki/Slide_rule#Logarithms_and_exponentials

That help?

Not really, I have a fealing I'm looking for the part where it uses logarithms to divide and multiply...

2009-06-05 07:20:48

#5

Surgeons: U shud proabbly f off u fat prik; +3,097|6913|Gogledd Cymru

SamBo:D wrote:
Slide rules are basically; one at a time and make sure the its clear at the bottom before you go down.

Also, if it's in a waterpark, wait for the green light/the lifeguard to tell you to go.

2009-06-05 07:25:42

#6

presidentsheep: Back to the Fuhrer; +208|6385|Places 'n such

Jenspm wrote:
presidentsheep wrote:
http://en.wikipedia.org/wiki/Slide_rule#Logarithms_and_exponentials

That help?
Not really, I have a fealing I'm looking for the part where it uses logarithms to divide and multiply...

Anything to do with the laws of logs?

log(ab)= log(a) + log(b)
log(a/b)= log(a) - log(b)
log(a^b)= bloga

I'd type my pc specs out all fancy again but teh mods would remove it. Again.

2009-06-05 07:38:50

#7

DrunkFace: Germans did 911; +427|7105|Disaster Free Zone

Didn't they stop using slide rules back in the 70's when they invented the calculator?

And what in gods fucked up earth are you doing an 'oral' presentation in maths for?

Also
log_ab = c
a^c = b

ie.
log₁₀100 = 2
10² = 100

Last edited by DrunkFace (2009-06-05 07:40:32)

2009-06-05 07:51:24

#8

Jenspm: penis; +1,716|7156|St. Andrews / Oslo

DrunkFace wrote:
Didn't they stop using slide rules back in the 70's when they invented the calculator?

yes.

DrunkFace wrote:
And what in gods fucked up earth are you doing an 'oral' presentation in maths for?

That's how we roll.

DrunkFace wrote:
Also
log_ab = c
a^c = b

ie.
log₁₀100 = 2
10² = 100

I know all that, I just can't figure out how it's used in a Slide Rule.

edit- k, the idea is that at the time of invention, they didn't have calculators. Therefore, multplying was a bitch, so they preffered to use a*b = 10^(lg a + lg b). They put this on this Slide Rule, because it's possible... or something, and could therefore easily multiply and divide.

I think I have the info I need now, but if anyone has anything to add, feel free.

Last edited by Jenspm (2009-06-05 11:56:11)

BF2S Forums Slide Rules and Logarithms

presidentsheep wrote:

SamBo:D wrote:

Jenspm wrote:

presidentsheep wrote:

DrunkFace wrote:

DrunkFace wrote:

DrunkFace wrote:

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