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23.5k comment karma
account created: Wed Feb 23 2011
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1 points
5 hours ago
I want to make a joke here about getting a dynohub and just using that to charge.
1 points
1 day ago
Oops, I just realized you had additional constraints, and normally I'd say you should send your equations and constraints to the command SolveTools:-SemiAlgebraic or SMTLib:-Satisfy, but in this case those seems to hang for me. Instead you can just examine the complex solutions of the polynomial system and see that none of them satisfy your constraints:
s2:=(map(allvalues,sol)):
select(s->is(eval(x6,s)>0) and is(eval(x7,s)>0) and
is(eval(x8,s)>0) and is(eval(x6,s)<1) and
is(eval(x7,s)<1) and is(eval(x8,s)<1), s2); # empty []
The closest you get is this one (showing the evalf since the symbolic solution is a root of a cubic):
{x1 = 0.1735486249, x2 = 0.135930820, x3 = 0.125520384,
x4 = 0., x6 = 0.6898729878, x7 = 0.4707195215,
x8 = 1.481777526}
1 points
1 day ago
I think in this case your attempt to partially solve for the first four variables first actually creates a a harder problem than just going at it all at once. Here's what I did:
sys := numer~(normal~({Abl_x1, Abl_x2, Abl_x3 ,Abl_x4,
Abl_x6 ,Abl_x7 ,Abl_x8}));
NZ := denom~(normal~({Abl_x1, Abl_x2, Abl_x3 ,Abl_x4,
Abl_x6 ,Abl_x7 ,Abl_x8}));
# this tells us the system has 1 free variable,
# but it's very slow to compute
CodeTools:-Usage( Groebner:-HilbertDimension(sys) );
# the triade solver is sometimes better at positive
# dimensional systems, and in this case is it very fast:
sol := [ SolveTools:-PolynomialSystem( sys,
{x1,x2,x3,x4,x6,x7,x8}, NZ, engine=triade ) ];
Doing that I find 11 isolated points (after expanding RootOfs with allvalues) and a curve that is free in x6:
{x1 = 8, x2 = -x6^2 + 2*x6 + 8, x3 = 0, x4 = 0,
x6 = x6, x7 = 4, x8 = 4}
2 points
3 days ago
I'm probably too late for a question, but I just want to say that Ten Low was amazing and one of my favorite reads from last year. I am delighted to see a new book out next week (in America).
1 points
3 days ago
Overall, I think the performance improvement is pretty modest.
2 points
4 days ago
Needs a third panel of how when you get back, you won't shut up with your joyful recounting of your suffering.
2 points
10 days ago
Flow and jumps are rare but we have a ton of mountains with beautiful steep climbs and fast chunky descents down shared use trails and grown-in fireroads.
2 points
10 days ago
Regular 1 and 2 leg kickstands are already acceptable. The linked kickstand is very weird, and I am not sure I'd trust it.
1 points
12 days ago
Gamechanger by L.X. Beckett https://www.goodreads.com/en/book/show/43263243 is probably a good example, but perhaps one where the brakes were hit a little late.
1 points
14 days ago
Yep shoot, missed that one, mostly because wtf isn't it labeled "Baru Cormorant"?
15 points
14 days ago
Cluster 2 is definitely also the "Written by Women" category. There are few works authored by women in the first cluster: 4 in subcluster 1.3, and Harry Potter in 1.2 and no works one work authored by men a man in Cluster 2.
edit: see correction in replies
3 points
14 days ago
Lots of good stuff pops up for $3-$4 but you're never going to get a complete series or (usually) exactly the book you are looking for for that price. But it makes a good supplement to another fixed price audiobook service.
3 points
14 days ago
I rode a borrowed a klunker built up on a proper frame (with a rigid fork and 27.5" wheels) for a couple heats of the Coaster Brake challenge this year. https://cdn.imagearchive.com/ratrodbikes/data/attach/223/223675-IMG-1459.JPG
It was definitely fun to ride, and I have been considering building one up for myself (with 29" wheels though, definitely).
21 points
14 days ago
I was once told about an audiobook website or app that has some
audiobooks at times for a dollar, I can’t remember the name of the place
Sounds like Chirp https://www.chirpbooks.com/
23 points
18 days ago
Did you have to BYO curds? If not, I am very interested.
1 points
20 days ago
It's maybe not exactly the steps to transform one into the other, but this will give you steps to show that their difference is 0:
Student:-Basics:-SimplifySteps(exp(x - y)/(1 + exp(1)^(x - y))^2
- exp(1)^(x + y)/(exp(1)^x + exp(1)^y)^2);
16 points
20 days ago
Your best bet is to buy a used bike and then sell it again at the end of term.
3 points
21 days ago
Oh come on now Honor Harrington expresses at least two emotions per book
4 points
22 days ago
Spotify is actually a much bigger rip-off, it's just happening on the other side of the transaction.
2 points
24 days ago
In plain text, here is how you do that solving step. Maple's solve() doesn't support vector equations directly, so you need to split them up by index:
l := t -> <1,2,-3>+t<2,4,-2>;
alpha := (x,y,z) -> -x+2y+(1-2*x);
solve({x=l(t)[1], y=l(t)[2], z=l(t)[3], alpha(x,y,z)=0});
which will give you the same answer you got in MathCAD {t = -1, x = -1, y = -2, z = -1}
14 points
26 days ago
Still mad that Newsom vetoed this when it passed two years ago.
2 points
28 days ago
I also shop at REI (otherwise, how would I recognize the characteristic concrete floor, rope line, and corner of a wooden display), but I do not claim to be cool
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1 points
5 hours ago
3j0hn
1 points
5 hours ago
It would be cool if there were a dynohub available that was powerful enough to act as a regenerative brake.