video thumbnail 1:14:54
What makes the natural log "natural"? | Lockdown math ep. 7

2020-05-08

[public] 737K views, 26.1K likes, 250 dislikes audio only

channel thumb3Blue1Brown

All about ln(x).

Full playlist: https://www.youtube.com/playlist?list=PLZHQObOWTQDP5CVelJJ1bNDouqrAhVPev

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Beautiful pictorial summary by @ThuyNganVu:

https://twitter.com/ThuyNganVu/status/1259288683489849344

Errors:

At minute 16, the sum should be written with a "..." to indicate going to infinity.

At minute 38, the exponent should have 1/(2s^2) instead of 1/s^2 for s to represent standard deviation.

At minute 54, an equal sign was mistakenly used in taking the derivative of x^3 / 3!.

At the end, it should be pointed out that the alternating series with x^n terms only converges for values of x between -1 and 1, so the values one can't be considered proven with values of x outside that range. Everything with the argument here is fine, as it only deals with the convergent input, but that fact should still be mentioned.

Related videos.

Calculus series:

https://www.youtube.com/playlist?list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr

The sum giving pi^2 / 6:

/youtube/video/d-o3eB9sfls

The sum giving pi / 4:

/youtube/video/NaL_Cb42WyY

/youtube/video/00w8gu2aL-w (Mathologer)

Thanks to these viewers for their contributions to translations

Hebrew: Omer Tuchfeld

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Video timeline (thanks to user "noonesperfect")

0:00:14 - Question 1

0:02:29 - Answer 1

0:06:27 - Prime nos. in Infinite Geometric Series (Basel problem) and their relationship with Natural logarithm

0:12:01 - More examples of prime numbers in infinite series and their relationship with ln

0:17:25 - Question 2

0:19:20 - Answer 2 and explanation using ln

0:22:25 - Question 3 and families of curves

0:26:37 - Answer 3 and explanation

0:28:50 - Imaginary exponential

0:30:57 - Derivatives of exponential terms

0:37:21 - Why derivative of e^t is the same as that e^t itself?

0:41:21 - Question 4

0:44:12 - Answer 4 and explanation using Python

0:46:02 - Taylor Series for e^x

0:48:29 - Derivatives of polynomial terms/Derivatives of e^x

0:50:56 - Derivative of natural logarithm using graph

0:56:07 - Question 5

0:57:37 - Answer 5 and explanation

1:02:15 - Euler–Mascheroni constant

1:08:37 - Question 6

1:12:41 - Connecting dots to the familiarity of different expression in math

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Question 1
/youtube/video/4PDoT7jtxmw?t=14
Answer 1
/youtube/video/4PDoT7jtxmw?t=149
Prime nos. in Infinite Geometric Series (Basel problem) and their relationship with Natural logarithm
/youtube/video/4PDoT7jtxmw?t=387
More examples of prime numbers in infinite series and their relationship with ln
/youtube/video/4PDoT7jtxmw?t=721
Question 2
/youtube/video/4PDoT7jtxmw?t=1045
Answer 2 and explanation using ln
/youtube/video/4PDoT7jtxmw?t=1160
Question 3 and families of curves
/youtube/video/4PDoT7jtxmw?t=1345
Answer 3 and explanation
/youtube/video/4PDoT7jtxmw?t=1597
Imaginary exponential
/youtube/video/4PDoT7jtxmw?t=1730
Derivatives of exponential terms
/youtube/video/4PDoT7jtxmw?t=1857
Why derivative of e^t is the same as that e^t itself?
/youtube/video/4PDoT7jtxmw?t=2241
Question 4
/youtube/video/4PDoT7jtxmw?t=2481
Answer 4 and explanation using Python
/youtube/video/4PDoT7jtxmw?t=2652
Taylor Series for e^x
/youtube/video/4PDoT7jtxmw?t=2762
Derivatives of polynomial terms/Derivatives of e^x
/youtube/video/4PDoT7jtxmw?t=2909
Derivative of natural logarithm using graph
/youtube/video/4PDoT7jtxmw?t=3056
Question 5
/youtube/video/4PDoT7jtxmw?t=3367
Answer 5 and explanation
/youtube/video/4PDoT7jtxmw?t=3457
Euler–Mascheroni constant
/youtube/video/4PDoT7jtxmw?t=3735
Question 6
/youtube/video/4PDoT7jtxmw?t=4117
Connecting dots to the familiarity of different expression in math
/youtube/video/4PDoT7jtxmw?t=4361