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## Natural logarithms

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## Calculator for natural logarithms

Calculator for Natural Logarithms
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## Calculator for natural logarithms

Discussion and questions for this video
ln = logarithmus naturali Latin not French.
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In french, ln = logarithme népérien, which translates to "Néper's logarithm'. Néper is a frenchization of Napier, as in john Napier (http://en.wikipedia.org/wiki/John_Napier), who invented logarithms.
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Why are ln and e so important?
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Invest $1.00 at 100% interest for 1 year. Compound: Quarterly:$2.44
Monthly: $2.61 100 times:$2.70
1,000 times: $2.72 10,000 times:$2.72
100,000 times: $2.72 1,000,000 times:$2.72

You eventually compound that one dollar so much annually that this is called "compounding continuously".
The value is approaching a limit called "e".

That's why e is so important. To compound continuously.

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Are there any videos are playlists specifically covering "e"?
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Thanks Marty! I looked and I found http://www.khanacademy.org/math/precalculus/v/introduction-to-compound-interest-and-e in case anyone else is looking.
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okay so, on the topic of natural logs, could there be some videos where the application of natural logs is necessary?
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you could try looking for videos of half-lifes and stuff because they use natural logs
hope this helps :)
1 Vote
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why is ln (-1) undefined??
1 Comment
Good Question!
It's the same as saying 'e' to what power equals negative one
e^x = -1
There is no real number for x that makes that equation true
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Actually it stands for "logarithme neperien" in frensh
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how do you find "ln" on a TI-84 plus calculator? if you can't, then how would you start to solve the problem 2e^2ln-4 - ln e^8 ?
1 Vote
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it's the button directly on the left of 4
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1 Vote
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how do i use the calculator for e to the 0.24?
1 Vote
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press the e button
press the ^ button
type in .24
press =
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At 0:45,what is mantisa
1 Vote
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The mantissa of a logarithm is the decimal portion of the answer. We usually speak of the mantissa when dealing with the common log rather than the natural log.

For example, log₁₀ (152) = 2.18184 (rounded off)
The mantissa is 0.18184...
The characteristic (which is the integer portion of the answer) is 2.

This is mostly just a curiosity nowadays, since calculators and computers have made needing to separate the characteristic and the mantissa obsolete.
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Find the interest of \$23,400 at 14.5% for 24 months
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1 Comment
If you get a question that says round to the nearest hundredth (for example) and you got a number like 1.1, would you have to put the extra zero at the end, or could you just keep it as 1.1 since the final zero is not needed?
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It is an issue of significant figures. If the numbers you are given have that accuracy, then there is a point to adding the zeros, additionally for computer-inputed answers. For paper grading without significant figure requirements it should not matter.
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C=2pier solve for r
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I am having trouble finding the correct answer on a calculator for P(t)=10000e^ln10/17 over 8 times 10? I'm not sure how to enter it. I have been playing around with examples and I am not coming up with the correct answer. Please help.
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I'm not sure if you mean (e^ln10)/17 or e^ln(10/17), but either way it works out the same. The natural log is defined as what power you need to raise e to to get a number, so e^ln of something is just that something. So we have 10,000*10/(17*8*10) = 10,000/(17*8) = 1,250/17. On a calculator, you would press the buttons like this:
10000
times
(
(
10
÷
17 (10/17)
)
ln(x) (natural log of 10/17)
)
= (10000 times the natural log of 10/17)
÷
80
=
1 Vote
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Could we please have some videos explaining more about what e is, where it came from, and how it's useful? Thanks!!
1 Vote
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Try watching sal's vids on "compound interest and e"
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what is the best way to deal with natural logarithm word problems?
any thing in particular i might want to look for?
even non-natural logarithms, what's a real life senario where they might apear?
1 Vote
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How do you deal with logarithms when placed in word problem form, or real life?
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I'm just wondering, but how does "e" show up in nature and finances?
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There is a connection to compound interest frequency, thats how the constant was discovered.
http://en.wikipedia.org/wiki/E_(mathematical_constant)#Compound_interest

One example where e occurs naturally is the capstan equation.
http://en.wikipedia.org/wiki/Capstan_equation
1 Vote
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so is there a section for natural logs like this: 1+LN(x)2=6 (one plus natural log x squared equals six)
1 Vote
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To solve that I would start by subtracting 1 from both sides.
1 Vote
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Report a mistake in the video
Example:

At 2:33, Sal said "single bonds" but meant "covalent bonds."

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