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<mbot> SAM_theman: m
<SAM_theman> 1
<SAM_theman> o
<SourceCode> @mbot DSolve[(t*T'[t] + 2*T[t])/T[t] == -B^2, T[t], t]
<mbot> SourceCode: {{T[t] -> t^(-2 - B^2)*C[1]}}
<SAM_theman> @math 7p=98p=7=7+5525235254(7)
<mbot> SAM_theman: 38676646785
<SAM_theman> wtf?
<lillpelle> SAM_theman: please learn howto do it before spamming...
<SAM_theman> yes Master
<apfel> I need to determine whether a decimal number (represented as a bitstring) is divisible by 7. I know that I can do it like this for the bitstring 1 100 010: 010=2, 100=4, 1=1, the sum is 2+4+1=7, hence it's divisible by 7. My problem is that I don't know the length of the bitstring in advance and I got to see the most significant bit first (i.e. read from left to right). Any ideas on how to adapt the described approach or any other ideas?
<SAM_theman> bbl
<_llll_> good grief
<Safrole> _III_ what's good grief? apfel's problem?
<buggler> ooooer
<buggler> if a number can be written as 7 * k
<buggler> then it can also be written as 10k - 3k
<buggler> and um that's all for now :P
<buggler> lol
<buggler> i thought it went somewhere but it didnt
<buggler> although i think it might lead somewhere!
<buggler> ooer from searching the web:
<buggler> To find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number.
<buggler> Example: If you had 203, you would double the last digit to get six, and subtract that from 20 to get 14. If you get an answer divisible by 7 (including zero), then the original number is divisible by seven. If you don't know the new number's divisibility, you can apply the rule again.
<buggler> 16394
<buggler> 1639 - 8 = 1631
<buggler> 163 - 2 = 161
<buggler> 16 - 2 = 14
<buggler> yay
<buggler> that's kinda awse
<apfel> The problem is that I need to create a deterministic finite automata which does the testing.
<apfel> For this DFA the above restrictions apply.
<apfel> But thanks for the tip. Never heard of this one. :)
<nANDy> Doesn't (mirrored E)x in S: A = False mean "there exists at least one x in S which makes A = False" and not "All x in S make A = False"?
<nANDy> it's in map theory
<SatanGolga> is there any #biology channels?
<Safrole> biology... ewww
<SatanGolga> :)
<SatanGolga> i'd take that as a no?
<Safrole> I wouldn't know
<Safrole> try EFNet
<Safrole> yeah there's #biology on EFNet
<Safrole> The room has like 10 people in there but it's something I suppose.
<joshk> haha
<SatanGolga> hehe, it's a start
<Safrole> bioinformatics... big ewww
<sdf> which log do calculators like Texas-Instrumrnt T83 have? log10 or log2 ?
<Spark> theres a #biology on quakenettoo
<SatanGolga> log10
<Spark> quakenet too
<sdf> and how can i het log2 SatanGolga ?
<Spark> try it out, do log 10 and see if you get 1
<sdf> get*
<sdf> yes 1
<sdf> but i need log2
<Spark> log(x) / log(2)
<SatanGolga> sorry don't know
<sdf> Spark thanks
<sdf> SatanGalga Spark knows it thanks both
<sdf> bye
<samch____> @math 77^7777
<mbot> samch____: 17312893855225627267011948536012032811706957723803252706569126231081
<mbot> 850653851\
<mbot> 29017958437788626310028961128608268202890464996042461114462869058681531628651\
<mbot> 41598488772773567618113353488765209851044962818943776650174982689358490479228\
<samch____> 99^9999^9999
<samch____> @math 99^9999^9999
<mbot> samch____: Overflow[]
<TheoMurpse> I'm trying to prove that the square of an integrable function is integrable. Any ideas?
<delta_> TheoMurpse, what does it mean?
<TheoMurpse> delta_ suppose you have a function f(x). f(x) is integrable. Now prove that (f(x))^2 is integrable
<delta_> TheoMurpse, it is integrable on what?
<TheoMurpse> That's precisely it
<TheoMurpse> The question is "Prove that a square of an integrable function is integrable"
<delta_> TheoMurpse, f is integrable on what space?
<Catfive> TheoMurpse - well, it's true but nontrivial that if f and g are integrable, so is fg.
<TheoMurpse> I ***ume it's over the reals. But it may just be over an interval of the reals
<delta_> TheoMurpse, could it be [0,1]?
<TheoMurpse> It's not restricted to [0,1]
<delta_> TheoMurpse, what do you think about 1/sqrt(x) prolongated by 0 eventually ;)
<TheoMurpse> Catfive, let me check my notes. I remember the prof saying that fact, but I want to verify if we can use it. Most likely not (as it was not proven in cl***), but it couldn't help.
<delta_> Catfive, it(s not true I think.
<Catfive> TheoMurpse - uh, well, if you can use it, your problem is trivial - take g = f. =)
<TheoMurpse> delta_ it's not a question of if the statement is true. It's a question from our text that we are required to prove is true, not prove if it is true or not.
<TheoMurpse> I've known about that 1/sqrt(x) thing, but I can't do anything about that.
<TheoMurpse> The question is not to prove/disprove, unfortunately.
<delta_> TheoMurpse, there is something I don't understand then. What do you think about rthe function I wrote up.
<Catfive> delta_ - if f and g are Riemann-integrable real functions of one real variable, it is certainly true that their product is also integrable.
<TheoMurpse> well 1/x is non-integrable over [0,1]
<TheoMurpse> so it fails in that case
<TheoMurpse> I should email the prof and ask him what he means by the question
<delta_> Catfive, how so.
<TheoMurpse> Because doing radical things like "this theorem is not in fact true because COUNTEREXAMPLE" is not looked upon happily. I got points taken off on a homework for disproving a theorem basically because "obviously, i didn't mean for you to consider this type of constriction" type thing
<TheoMurpse> Grader is an ***hole
<TheoMurpse> Also, Catfive i cannot use that fact, buecase another hw problem was "prove that the product of integrable functions is integrable"
<delta_> TheoMurpse, maybe the setting is slightly more precise.
<TheoMurpse> and we USED the fact that the square of an integrable function is integrable to prove it
<delta_> Catfive, forget what I wrote ;)
<Catfive> delta_ - already did. =)
<nytejade][LOB> If I have a number in a base-X positional number system for positive integers and (130)ba*** = (28)base10, how can I find the value of X ? (x is a positive number)
<TheoMurpse> well, i've emailed the prof and am awaiting his reply.
<TheoMurpse> How about prove that if f:[a,b}->R is increasing then the integral from a to b of f(x)dx exists.
<Nomius> Does anyone have a link where explain how a poisson distribution approximates to a normal distribution?
<Catfive> TheoMurpse - that is considerably easier.
<TheoMurpse> Yet also difficult. I thought that if it was bounded that the function must be discontinuous at finite amount of points, but it turns out that is not the case. So I'm stuck.
<Catfive> TheoMurpse - first note that f is necessarily bounded on [a, b]. Then consider a partition of [a, b] into n subintervals of length delta, and look at the upper and lower sums U(f,P) and L(f,P). Finally, come up with an expression for U(f,P) - L(f,P).
<TheoMurpse> We don't know about upper and lower sums
<delta_> Catfive, it's just wrong though :). Anyway ;)
<Catfive> delta_ - hmm?
<TheoMurpse> catfive we don't know about upper and lower sums. However, we do have a theorem that states that f is integrable iff there are step functiosn f1 and f2 such that forall x, f1<f<f2 and int(f2,a..b)-int(f1,a..b)<epsilon forall epsilon
<TheoMurpse> Our definition for an integral is if f(x) is integrable over a..b then forall e there exists d such that |S-int(f(x),a..b)| < e forall riemann sums S with width <d
<liquid> hi .. i need some help with solving 3 simultaneous equations as a parametric equation. ive tried for about 40 mins, but cant get my head round it. can anyone help me?
<liquid> here are the equations: 2x-y=1 & 3x+2z=13 & 3y+4z=23
<liquid> i tried using a matrix to solve them, but the determinant was 0, so there were either infinite or no solutions...
<liquid> then i tried to solve via elimination, but couldn't get very far
<liquid> can anyone help me with this problem?
<liquid> is there anyone around?
<Tirlasmisu> not exactly sure what you mean by "as a parametric equation"
<Tirlasmisu> My understanding is y=f(t) and x=g(t)
<Tirlasmisu> are you trying to solve for values of x,y,z?
<liquid> yes... the aim is to express x y and z as a parameter
<Tirlasmisu> hmm
<liquid> let me rephrase... the aim is to express x y and z as functions of the same parameter
<liquid> the answer that is in the back of my text book seems wrong to me, but then again i have just started learning this... so im not sure
<lillpelle> liquid: the anwer may look different depending on what parameter you choose
<liquid> Tirlasmisu - any ideas?
<liquid> ah ok...
<liquid> so, if i chose z = t, it would be different if x=t>
<liquid> is that the idea?
<Tirlasmisu> yeah
<lillpelle> liquid: yes
<lillpelle> liquid: did you choose z=t?
<liquid> that is what i ***umed to start with, however, in the final answer, neither x y or z = t
<liquid> thats what is confusing me
<liquid> the answers they give for x, y and z respectively are: 2t+1, 4t+1, and -3t+5
<liquid> i feel this is wrong because there is no common point of intersection of the given answers
<delta_> liquid, do you know Gauss resolution method to solve a linear system of equations?
<liquid> yes - i tried using that too
<delta_> liquid, it must work.
<liquid> it does, but the answer i get does not coincide with the given answer
<liquid> delta_ : would you try solving the 3 simultaneous equations i typed earlier
<liquid> here are the equations: 2x-y=1 & 3x+2z=13 & 3y+4z=23
<delta_> liquid, I could try but, you might also briefly check your answer is solution of this system, could you?
<liquid> i dont understand...
<liquid> oh i see
<mads-> How many digits are there in (4^8)*(5^17) ? Calculators not allowed.. =/
<Prof_Vince> hint: 4 = 2^2
<liquid> delta_, as a request, could you try as well, and perhaps work through it ;)
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