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jarlemag

 Mathematics

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jarlemag
Nov 25, 2020 22:51
Thanks for the help! I'll take a look.
jarlemag
Nov 25, 2020 22:47
@Semiclassical Interesting! Can you give any more clues? :-D
jarlemag
Nov 25, 2020 22:44
Uh, I hope I remembered that trignometric identity right...
jarlemag
Nov 25, 2020 22:43
@Semimclassical: I tried to solve it this way before reading the questions/answers mentioned, but it doesn't seem to give right results. If anyone can see something obviously wrong, I'd be happy to learn where I misstepped:

α is an angle in the XY plane (angle from the X axis), β is an angle between the XY plane and the Z axis. Find the corresponding unit vector v.

We know that:
x^2 + y^2 + z^2 = 1

Let f be the length of the projection of v into the XY plane. Then:

sqrt(f) = sqrt(x^2 + y^2)
jarlemag
Nov 25, 2020 22:22
I think this would be a statement applicable to my case: "α is an angle in the XY plane (angle from the X axis), β is an angle between the XY plane and the Z axis. Find the unit vector with direction defined by the angles.
jarlemag
Nov 25, 2020 22:16
I got a bit confused by the question (and a similar one here: stackoverflow.com/questions/30011741/…) too, but the basic question is still "how to get (unit) vector from two angles."...
jarlemag
Nov 25, 2020 22:05
Hi. Does anyone know where I could find a proof/explanation of this answer about how to Calculate 3D Vector out of two angles and vector length?
https://math.stackexchange.com/questions/1385137/calculate-3d-vector-out-of-two-angles-and-vector-length
jarlemag
May 20, 2015 21:34
Not that it matters much, was just curious how much effort they actually put into the ad.
jarlemag
May 20, 2015 21:33
Still, I wasn't sure if the notes actually make mathematical sense...
jarlemag
May 20, 2015 21:32
Ted Shifrin: That was my understanding too. Studied both Fourier and Laplace transforms in Uni, but that's a while ago. :)
jarlemag
May 20, 2015 21:30
pjs36: Do you mean the top line?
jarlemag
May 20, 2015 21:29
Hehe, OK.
jarlemag
May 20, 2015 21:28
Bigger version here: scontent-ams2-1.xx.fbcdn.net/hphotos-xta1/v/t1.0-9/…
jarlemag
May 20, 2015 21:27
What about the next lines, any ideas?
jarlemag
May 20, 2015 21:27
Yes, I thought so. But wasn't entirely sure there wasn't something else using similar symbols.
jarlemag
May 20, 2015 21:26
We're getting closer!
jarlemag
May 20, 2015 21:25
Ahem, that's beside the paper...
jarlemag
May 20, 2015 21:25
Can anyone say what's on the paper in this pic? : scontent-ams2-1.xx.fbcdn.net/hphotos-xta1/v/t1.0-9/p320x320/…
jarlemag
Mar 15, 2015 15:56
Hi everyone: I've posted a question about a simple stats problem dealing with determining minimum sample size. If anyone can check my thinking it would be much appreciated: math.stackexchange.com/questions/1190848/…
jarlemag
Mar 15, 2015 13:12
(Assuming a significance level of 5%)
jarlemag
Mar 15, 2015 13:11
Treating the poll as a binomial test approximated by the normal distribution, I arrived at n>= 1373.
jarlemag
Mar 15, 2015 13:11
Hi. I wonder if someone could help me check my answer for an exercise: Assume that 28 % of voters favored party A at some point. A later opinion poll gave a result of 30 % of voters favoring part A. What is the minimum sample size allowing us to discard the null hypothesis of no change in voter preference?
 

 Discussion on question by David Zhang…

Imported from a comment discussion on philosophy.stackexchange...
jarlemag
Feb 22, 2017 20:54
You may want to check out the following blog post: How many lives does a doctor save? 80000hours.org/blog/72-how-many-lives-does-a-doctor-save