#help-43
1 messages · Page 42 of 1
you can notice that ||CQ bisects <PCM (you probably already know this) and MQ bisects <PMC (given in the statement). So what do these 2 things imply?||
@icy topaz Has your question been resolved?
That Q is the incentre of the triangle PMC
yeah
this should allow you to angle chase and find <PQC
then you can do this
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adding x^3 and subtracting x^3 to that first integral
and then i thought x^3-sin^3x ill write as (x-sinx)(x^2+sin^2x+xsinx)
but i didnt know what to do from there
@native shard
should be + xsinx
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Do you know the formula for summing the natural numbers from 1 to n?
n(n+1)/2
can you elaborate
$\sum_{i = 1}^n ki = k\sum_{i = 1}^n i$
VulcanOne
You will need to use this fact to deconstruct the summation
And make it easier to use the formula
Also
$\sum_{k=1}^n \left(k + c\right) = \left(\sum_{k=1}^n k\right) + \left(c\sum_{k=1}^n 1\right)$
VulcanOne
You will need to focus on the problem so I can help
I am focused, 100%
im here dude
I gave you the 2 most important facts for Q 3
Fact 1
Fact 2
how ?
I want you to reach the answer by yourself Renato
There you go renato
@twin idol
how?
ii has a bit of a trick up its sleeve
dude HELP

That's correct
You did well
Now are you able to do 2 in the same way?
Yeah
Can you do it in the same way?
I'll need to give you another fact
Because of the trick
$\sum_{k=c}^n k = \left(\sum_{k=1}^n k \right) - \left(\sum_{k=1}^c k\right)$
VulcanOne
the problem is that the starting index is 6 not 1 dude
Yeah that's what the fact is for
Fact 3
@twin idol
are you in osu dude?
Alright nice
That's great
?
I won't have access to my laptop
how
Well
please elaborate
The same formula you used for $\sum_{k=1}^n 5$
VulcanOne
But instead of n it will be 6
$\sum_{k=1}^6 5$
VulcanOne
Evaluate it
5*6
Yeah
lmfao
Correct
Now we can get into Q4
Stop asking this! Be patient!!
!noping
Please do not ping individual helpers unprompted.
what is the trick to q4?
And if you really want to ping, do it once
Because this sounds very very bad-manner, even if it's not your intention
you can always use discord from the phone
He's gonna be at work
for a week straight
I didnt know
Alright. Please tone it down with the pings
Alright now let's move on to Q4
$\sum_{k=0}^{n-1} p^k = \frac{1-p^n}{1-p}$
VulcanOne
Fact 4
I dont think I can take this as true
Why not?
This is the sum of a geometric series from k = 0 to n-1
well
I gave you the sum with different indices. It's a correct formula.
Use this as fact 4
how did you came up with this?
The geometric sum formula is used to calculate the sum of the terms in the geometric sequence. Understand the geometric sum formula with Derivations, Examples, and FAQs.
Use this as fact 4
Check the proof after scrolling down
Buddy I'll have to leave now. I gotta do some stuff before going to work
$\sum_{k=0}^{n-1} p^k = \frac{1-p^n}{1-p}$
Renato
VulcanOne
Same thing
Anyways gotta leave now
Good luck. You can do this on your own I know that

have fun at work dude, ping me if you want to osu
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Did I set this up right?
do Win + Shift + S to take screenshots
also, go show your answers for (a) through (d) before we consider (e)
A. 15,957 B.797.85 C.”It measures the rate of change of people” D.9092.15
(c) is too vague, theres multiple ways to measure that rate of change
you need to be specific that its the average rate of change from 1980 to 2000
(d) btw is exactly the same as (b)
Alright so we’re back on question e
you know why (d) = (b), right?
The average rate of change divided by 20 right?
the average rate of change already includes a /20, as you did in (b), so no
you dont divide the average rate of change by 20 a second time
do you know what average rate of change is
797.85
a number isnt going to convince me you know why its supposed to be like that
where did you even get 9092.15 from
oh alr, thats wrong but I see you wont be doing that anymore
now for this
unless youre a fan of writing down numbers with decimals on paper all the time, we gotta get the calculator to do this for us
i got desmos pulled up
now the best-case scenario is telling the calculator a and b and it tells us back the average rate of change
to do this, we have to make something that can calculate this
sort of plan the calculation out
lets say youre figuring out the average rate of change on [5, 10]
what would you calculate to get this answer?
797.85-2000/10-5?
lets look at the numerator again
also dont forget ()s
for average rate of change on [5, 10], you need (something) / (10 - 5)
797.85 - 2000 is not the correct idea
we're nto considering average rate of change of average rates of change
first,
do you understand this part of the problem
That's the formula I should be using
surely theres more to P(t) than "oooh its a formula"
maybe that it means something about the population?
p(t)=population
P(5) represents the population in what year?
1985?
yea
try redoing this using P(t)
(1985-1.04) / (10 - 5)?
I thought thats why u asked me this
Im asking you that because, no, you dont just put 1985 - 1.04 for the numerator
lets try something else
earlier you said P(5) means the population in 1985
so we have a way to go between 5 and the year 1985
based on that, [5, 10] represents what 5-year span?
1980
1980 is not a "5-year span"
1980 is just a single year
lets restart
10, what year does this represent?
(you already know 5 represents the year 1985)
1990
1985-1990
so where did this come from?
I went backwards instead of forward
??????????????
thats a bold move
anyways [5, 10] represents 1985 to 1990
so since P(t) represents the population in 1980 + t,
P(5) represents the 1985 population
P(10) represents the 1990 population
(1990-1985) / (10 - 5)?
those are just the years
thats 1
thats saying 1 year happens every year, on average
think about what youre doing
mb
let me continue
so P(5) tells us the population at the beginning of [5, 10]
and P(10) tells us the population at the end of [5, 10]
we know the years that these represent, but we dont need to use that information for now
I was just giving context for what this (otherwise vague) thing means
you understand these, right
P(5) is the population at the beginning of the interval [5,10]
right
we can calculate P(5) to be 185444
and P(10) to be 189117
so whats the average rate of change for the population from 1985 to 1990?
where did u get these numbers from 185444 189117
ok you dont understand this then
I want you to actually know what this image means
read this closely, what does this mean?
theres not like a hidden message or anything, I just want you to know what P(t) even is supposed to be about
you just multiplied 181843(1.04) and got 189117
so you just replaced t with 10 and did the same with 5?
yes, thats how you use a function
moving on,
185444 is the population in 1985
189117 is the population in 1990
so whats the average rate of change in population from 1985 to 1990?
going to remind you btw that you didnt have a problem with this problem when it was phrased like (b), so this time you have no excuse
look back on the calculation you did for (b) if youre stuck on finding this rate of change
734.6
there you go
now lets consider another problem with the way we're doing things
remember that we were trying to plan out a calculation, right?
yes
when I ask, all youre giving are the ending results
you didnt show what you did
we cant plan just on the final result
how do i sc again
Win + Shift + S
theres an option in the windows settings to remap this to the PrntScreen button, if you want
not sure if itll do the same thing though
last time I checked, PrntScrn copies your entire screen to your clipboard
mb
select an option at the top of the Win + Shift + S menu to change which kind of selecting you can
default option is whole screen, but you can also chosoe to screenshot a window or screenshot a rectangle of your choice
Im screenshotting rectangles with Win + Shift + S to get my pictures
ok thanks
anyways for here, small change we gotta do for convenience later
we change the denominator to 10 - 5 instead
that way, its closer to the t we used
10 - 5 and 1990 - 1985 both calculate a 5-year difference
since the units are in years
now for the final change
189117 and 185444 werent just any numbers
we had to calculate them, from a formula
what function gave us those two numbers?
you dont have to write out the whole formula or anything, you can just mention the function
dw
youre being precise
youre forgetting ()s though, ^(t/10) instead
and that t should be a 10 as well
wouldnt that just be 1 for 10?
alr
we're going to leave that up to the calculator
really, this is our formula
keep in mind what we based this all on: (b)
(b) had you do the same kind of calculation for the average rate of change
now we see the same formula again, but for P
(P(b) - P(a)) / (b - a) finds the average rate of change of the function P from a to b
on [a, b]
this is an example for [5, 10]
from here, Ill show you two ways you can get the calculator to calculate this
ok
first, by default desmos doesnt know what P is
define the function P in a separate line
desmos then knows that its a function, so P(5) and P(10) can be calculated
for desmos in particular, use x for the input variable
using another variable (like t) might mess things up if you use t for something else
to further shorten how much we need to do, replace 5 and 10 with a and b
that way instead of replacing both 10s with 9s, you can just replace the =10 with =9
yep
theres a closely-related second way to this
take a look at the guess you started with
I dont understand how you cooked any of this to the way it is
but does look like you want to reduce it all into as few lines as possible
all in one big formula
Trial and Tribulations
little too advanced for me
compared to the previous one, theres a lot more going on here, but its the same calculation
first
this is a function that takes in two inputs
it is written f(x, y)
f(5, 10) will have the input x=5 and y=10
yes?
yes
second
this is just P(y) - P(x), isnt it
you dont seem to recognize it given your immediate reaction
yeah but i probably wouldnt come up with this on my own
my brother in christ, you copy-paste P into there
you can come up with copy-pasting
thats all I did, nothing more
youre seeing what Im seeing right? I didnt do any further steps than just writing down P(t) into there
yes i can see that
wdym "come up"?
like for me I see all the steps i did to come up with answer to actually understand it
well we didnt reach the final step yet
so you mean this for the whole formula then
wym
sure
final thing, instead of a and b we use x and y
no big reason other than for desmos to like it better
yep
we made the function so that you can do that
f(5, 10) for [5, 10]
you can also see the function so you can be sure that its calculating the right thing
its doing (P(y) - P(x)) / (y - x) for the x and y you put in
(P(a) - P(b)) / (a - b) also works
you can multiply by -1 / -1 to swap between this and the other one (P(b) - (a)) / (b - a)
But what I did is correct right?
yea
Alright thank you so much for your help idk how u put up with me I was trying but some of this just didn't make sense to me
and im just using my calculations i used for part E on part F right?
(f) has you do something different
consider this
(f) wants you to consider how the numbers change as you go from [5, 10] down to [5, 6]
then use that to guess what the "instant" rate of change at 1985 is
now f(5, 5) wont work, since thats a rate of change with / (5 - 5) which divides by 0
so they want you to roughly estimate it from these
Its getting closer to 727
you can also just do f(5, number really close to 5)
it gets close to 727.596
Im not too sure what they mean by the second question
yep
second question, it should just be P(6) - P(5) but not sure on why theyre just asking you to do that
seems too easy
but it should be correct
Alright thank you
np
Don't go to far ill be back tomorrow your one of the best tutors I've ever had
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I need help with part 2 of question 1.5. This is real analysis 1
<@&286206848099549185>
have you tried anything yet?
Yes
I’ll send it right now
I think it’s wrong though
Would you like to see my professor’s hints?
hm, you're picking z to be an element of X, but that isn't what we want to prove 
you are claiming that sup(X) = 1/3, right? why not find the difference between 1/3 and f(x) in terms of x?
we'd like to show that if s > z, then z isn't an upper bound of X - that's not the same as proving that no element of X is an upper bound for X
We haven’t learned functions yet @upper bane
replace f(x) with that expression
Huh?
I’m just confused where to start
And where to go
you assumed that z has the form (x^2 - 1)/(3x^2 - 1), when this doesn't have to be the case 
as for what to do, Hanako's suggestion is useful
the idea is, you want to prove that sup(X) = 1/3, so you have to prove that there is no z < 1/3 that is an upper bound
Here’s what my professor wants me to do
from here, find the difference between 1/3 and the expression.
then, let z < 1/3 and set $\epsilon$ = 1/3 - z > 0
Hanako
from there, the difference between 1/3 - z is exactly the difference between 1/3 and the expression found earlier
and we want this difference to be smaller than epsilon
here's a more explicit plan of action:
first, prove that the sequence (n^2 - 1)/(3n^2 - 1) converges to 1/3. spoilers for the rest: ||then if z < 1/3, the distance from 1/3 to z, given by the difference |1/3 - z|, is equal to some positive number epsilon. but since that sequence converges to 1/3, the difference between (n^2 - 1)/(3n^2 - 1) and 1/3 goes to 0 as n goes to infinity, so for a sufficiently large value of N, you can pick an element of X that's larger than z (distance to 1/3 is less than epsilon), hence z isn't an upper bound.||
I can’t use sequences
It’s like very limiting with what I can use
The definition of LUB
And ordered sets
The hints doc I sent pics of lays out kinda what I should do
Also, Archimedean property could be useful
I must apologize for misleading you then 
I don't think I can figure out a way to do this problem with what you have 
Then what should I do
I’ve been stuck on this one
I can show a problem where I proved GLB, which might help
<@&286206848099549185>
?
I need help with this analysis problem, and other people can’t figure out how to do it with my current level of knowledge
@hushed tapir Has your question been resolved?
can you repost the question and your progress so far
im not sure how far youve gotten
It deals with smth like this
I only proved that it’s a upper bound, not that it’s a LUB
okay, cool
there's 2 ways to show that an upper bound s is a LUB
way 1: show that all other upper bounds are >= s
way 2: show that any number < s is not an upper bound
I think way 2 is easier here
That’s what the professor said
let's try that then
Did you read the hints?
let's take some number less than s. call it s - ε for some ε > 0
no, do you want me to? i have a fairly certain idea of how to go about this but if theres a specific way you want this done we can look at that
Can you? It’ll give kinda an idea of how he wants it. I only just started analysis so we have learned: ordered sets, LUB GLB, BFA, and archemdian property
Yeah, it’s typed
everything they said seems pretty reasonable and normal
i dont think theres a special way you have to do this
So what should I start doing
I have that already, I called it z
we want to show that for some n in N, (n^2 - 1)/(3n^2 - 1) > 1/3 - ε
i think it might be easier to work with 1/3 - ε instead of z
because then you isolate a positive part and the limiting part
Why would that prove this
are you asking why we want to show that for some n, (n^2 - 1)/(3n^2 - 1) > 1/3 - ε ?
or why i decomposed it
into 1/3 and ε
So you’re saying trying to find an x s.t. It’s inbetween the LUB and some variable ε
no, let's just use your z variable
(sorry to bother, but when you're done, snowflake, could you pls look in bots and see if my version works? thank you, and sorry for imposing. it's ok if you can't though!)
i want to show that for any z < 1/3,
(n^2 - 1)/(3n^2 - 1) > z
for some n. I just want to show that z isn't an upper bound, and this is the definition of that
okay great. it's just equivalent that if z < 1/3, then I can write z as 1/3 - ε for some ε > 0, and then the inequality just becomes finding n such that
(n^2 - 1)/(3n^2 - 1) > 1/3 - ε
which is equivalent to finding n such that
ε > 1/3 - (n^2 - 1)/(3n^2 - 1)
and it's generally easier to aim for something to become arbitrarily small/close to 0 than to work around an annoying variable like z that has implicit stuff floating around it
that's just the motivation I had for decomposing it, it makes things a little more straightforward this way
for all ε > 0, we just need to find some n such that 1/3 - (n^2 - 1)/(3n^2 - 1) < ε
do you still follow
Yes
great
Let me write down you’re thinking real quick
Why are we allowed to make this equality
We don’t know if such n exists yet
this is the goal, we don't know this works yet
the goal is to obtain an n that makes this true
if it does, then we've found an n that disproves 1/3 - ε being an upper bound
if we can do this for arbitrary ε, then 1/3 must be the LUB
a common method (the common method) in analysis is to "work backwards" from inequalities that you want to be true, to solve for appropriate conditions that make them true
since for each ε, we only need to find a single n that satisfies the inequality, we have a good amount of flexibility to solve for valid n
does that makes sense
Yeah, so we use the inequality we want to be true to solve for something? That seems circular
no
we are not using the inequality at all yet
we are going to use basic facts to prove the inequality for some n first
then, we can use the inequality to prove our claim that 1/3 is the LUB
the trick here though is that often times, operations on inequalities and equations are "invertible"
we can obtain equivalent inequalities by adding the same thing to both sides for instance, or multiplying by a nonzero number
the idea is if we can do some "allowable" manipulations to this inequality, constantly "thinking backwards" about what these manipulations imply, then we can eventually find some n that will directly imply the original inequality
you did this all the time in grade school
when i want to solve 3x > 18 for x, I first look at 3x > 18, and then divide by 3 to get x > 6, right?
maybe that seems circular. I started with 3x > 18 to find x values that satisfy 3x > 18, how does that work?
well, because dividing by 3 is an invertible operation on inequalities, I knew I could always just work backwards from wherever I end up to get the inequality I wanted
we havent even gotten to the solving step yet
are you okay with this
Yeah
It’s the goal?
yes
but we're gonna try manipulating it directly first
in ways that we can easily reverse
or at least reason about
so that we can find valid n that we can apply the steps in reverse for to get the desired goal
so let's start manipulating it
Yes!
ideally, we get the n by itself
a polynomial / a polynomial is pretty annoying
do you have any ideas on how to make it simpler
We should create a simpler rational fraction
yup
that isn't something we can legally do though
we need valid operations
you could potentially make an argument to do that, what would your argument be
right, youre close already
just finish this thought
n^2-1/3n^2-1 > n^2-1/3n^2
if that was true, that wouldnt be helpful for us
if I only know that c < a, I can't use c in any way to prove that a < b
if c > a, then i could just prove c < b to show a < b
the issue is that this isnt true
Why?
I didn’t include parenthesis, want me to rewrite
Yeah but my computer is far and my roommate is sleeping
parentheses would be rlly helpful yeah
$\frac{n^2 - 1}{3n^2-1} > \frac{n^2-1}{3n^2}$
snowflake
this is what you wrote right
Yes
okay perfect
yes this is true
now how can we manipulate this to relate to our goal inequality
reminder that this is our goal inequality
no we dont
just look at the LHS
our goal was to simplify it right
Yes
and we said that (n^2 -1)/(3n^2) is smaller than (n^2 - 1)/(3n^2 - 1)
Yes
if i subtract a smaller thing from the same number, whats the effect on the overall difference
Huh?
you can figure this out
if $a < b$, then what's the relationship between $x-a$ and $x-b$
snowflake
x-a bigger
yes
and we can prove that from simple inequality rules, multiply by -1 on both sides and add x
so with that in mind, what does the inequality look like with 1/3 and our rational expression
1/3 greater than our expression?
$\frac{1}{3} - \frac{n^2 - 1}{3n^2-1} < \frac{1}{3} - \frac{n^2-1}{3n^2}$
snowflake
Yes!
do you see why we care about doing this
Not really
we wanted to show that the LHS was < ε right
Yeah
what can we instead show now
this is still our goal
instead of showing this directly
we can do something else that will prove this indirectly
What’s transitivity of inequalities
if a < b and b < c then a < c
But our new inequality is bigger, so how would that help
based on this
I feel so stupid, I’m really confused. I get the idea of using another inequity but idk how that applies here
okay, so we had our original quantity a (a is our 1/3 - fraction).
we want to show that it's smaller than this other quantity c (c is epsilon).
we found a new quantity b that's bigger than a (b is 1/3 - the new fraction).
if we can show that b is smaller than c, and we know that b is bigger than a, then a must also be smaller than c
right now, we know b is bigger than a, so all we need to do is show that b is smaller than c. if we can do that, then we've indirectly proven that a is smaller than c
and a < c is our goal
Yes!
so what do we want to prove right now
1/3 - new fraction is less than ε
perfect
in other words, we need to find n such that $\frac{1}{3} - \frac{n^2 - 1}{3n^2} < \epsilon$
snowflake
Yes
what are your ideas to do next
Solve for n in terms of epsilon
Make a new inequality?
(do you see how to solve from here)
no
we can solve from this one
what is the literal first step we can take right now
why was it helpful to get rid of that -1 in the denom
Distribute
exactly
after doing that and simplifying, what do we get as our new equivalent condition for n
But we are using something we are trying to prove
yes, distributing is a reversible operation
No, I mean with the epsilon and stuff
so i know i can undo my steps once I can get to n
we haven't specified anything on epsilon yet
its fully arbitrary still
and our n is allowed to depend on epsilon
we're trying to prove that for all epsilon, there exists some n such that the inequality holds
so that n can intrinsically depend on the specific epsilon
our goal was to show that inequality right? if we can apply a series of reversible steps to reach a direct constraint on n based on the given epsilon, then for that epsilon, we can find a specific value of n and work backwards to show that the inequality holds
it might make more sense once we finish
n > right
that seems good to me
so after applying our reversible steps, we got that n should be > sqrt(1/(3ε))
because all of our steps were reversible, this means that if n > sqrt(1/(3ε)), then (n^2 - 1)/(3n^2) > 1/3 - ε, meaning that (n^2 - 1)/(3n^2 - 1) > 1/3 - ε, proving that the RHS isn't an upper bound
you can easily verify that this is true by proving this starting from n > sqrt(1/(3ε)). we just don't have to because all of our steps were reversible
Huh
So we found an inequality satisfying n, so we using the transitive properties of inequalities to show that since n exists, then the inequality exists
we found an inequality describing the necessary conditions on n for our goal inequality to be true
and then yes, we showed the goal inequality through transitivity using our modified inequality
pick some integer n such that n > sqrt(1/(3ε))
then it follows that 1/3 - ε is less than that corresponding element of the set
that's basically it
So what did that prove
In that since we found a condition for n, then 1/3 must be the sup
we proved that every number less than 1/3 isnt an upper bound
since you already showed 1/3 is an upper bound, that makes 1/3 the least upper bound
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Help needed
What do you mean by max value of x + y + z
When they are complex
@wheat seal Has your question been resolved?
- Real numbers are complex
- The imaginary parts can cancel
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Well every element of H has odd order
well, how
Lagrange's theorem
order of element divides order of group
ah right
Lemme prove that
right
follows from the order of a group, divides the order of it's subgroups
The other way
oops yea
Infty
order of an element is never 0
@carmine garden Has your question been resolved?
yeah I just realised what to do
note that having a subgroup of order 4 isnt the same as having an element of order 4 -- the latter property is stronger!
We have each interior angle is $\frac{180 (n-2)}{n}$
wai
I'm trying to come up with a rotation of order 3
why 3
correct but useless
I have to have the 0 rotation
a rotation of order 3 cannot possibly belong to a subgroup of order 4
a 180° rotation does generate a subgroup of order 2 indeed
have you tried it
btw you are currently talking about a group generated by vertical refleciton, horizontal reflection and 180° rotation?
No
I have a n-gon
I'm looking at a dihedral group of order n where n is an even integer
And it's subgroups of order 4
Yeah, and by adding a vertical and horizontal reflection, what did you mean?
you had a group generated by 180° rotation (this one was of order 2)
and you wanna add vertical and horizontal reflection now?
That could add way more elements than you think
unless you intend to add only vertical and horizontal reflection, in which case you should recheck the definition of a group
I mean a vertical reflection done two times brings us back to where we started
yeah, its an element of order 2
Well a horizontal reflection , followed by a vertical reflection won't bring me back to any of the elements in the group
indeed
doesnt satisfy the closure axiom if that's how you call it
seems like you'll have to do a small tweak
for any two differents elements of order 2: a and b, ab is not the identity
Btw in general, if you want to add some elements to your group / subgroup, then the smallest subgroup closed under the group operation is the one generated by the elements you added (+ elements or generators of the og subgroup). That's why i thought you meant generating
I see what you mean
Oh
Got it
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How to do this
I tried transferring 5 and 13 to other side
Then make a polynomial q(x)
= p(5x) + p(x) - 18
That didn't give any ideas
Can anyone give more strategies?
I also have a solution but I failed to understand
Can anyone explain that too?
Let $r$ be the integer root. Then, $$p(x)=(x-r)q(x)$$ for some polynomial $q$ with integer coefficients.
Civil Service Pigeon
Further hint (this gives away a lot): It follows that ||10-r divides 5|| and ||2-r divides 13||
Я не вижу такого решения 
Ok sir
On it
Interesting
Ok got it sir
Can I share the solution?
well I kinda need to see the solution to explain it
and you also need to be specific about what part you don't understand
Ok
Why write p(r) as that?
What is the intuition?
How will one come up with it
this is translating "integer coefficients with at least one integral root" into math
and they give you p when x=2 and x=10
so it's natural to put in those two values
and at this point you see it and go
oh
question done sans number crunching
yay
Huh?
they're using a somewhat similar idea here
Oh
except they're trying to make a polynomial that's equal to zero at x=2 rather than 13
because 0 is generally nice to work with
not that it really matters
Wait a minute
So they are trying to make a polynomial just as I did?
What is the difference in their and my formation?
I explained their formation using the logic I used since they're basically identical
idk what your intuition was tbh
I mentioned it
Oh
Just make a polynomial that is 0 at 2
Ig you're trying to combine the conditions into one?
but a lot of the time you lose information that way
ex. Let's say you're given a=7 and b=5
then you know a+b=12
but if you now only work with a+b=12, you have now lost information
because you can no longer deduce the values of a, b with just a+b=12
(r-2)q(r) = -13
q(r) is an integer because q has integer coefficients
aka you have two integers multiplying to -13
13 is more restrictive since it's prime
fewer possibilities for factors
so it's easier to narrow down with that first
before turning to p(10)
Oh i see now
My vision is clearer
You idea was way smarter
It would make r restricted to only a multiple of something
Sorry not r
X
yeah this is a classic case of "do the easy stuff first because if it doesn't work, you didn't waste that long. but if it turns out to be the main idea and you glossed over it, well then you feel like shit"
the easy stuff being rewriting the condition as p(x)=(x-r)q(x) and plugging in the values of x corresponding to the given values of p

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can somebody see if this proof is correct , if it has errors , where and how can i fix it please? Appreciated much.
hello, we'd prefer screenshot lest the link is malicious.
sorry will do
!nopdf
nah, I don't like to use factoids.
Why f,g continuous on I?
I know it's not the proof part but I don't think it's necessary, is it?
I suppose its not neccesary as it will follow from them being differentiable.
No, it does not at a
True, i suppose it needs to be continuous at a for some reason, but im not sure what
I don't think it needs to; anyway, it's probably irrelevant
Yeah its just what it said in my book for the theorem
Oh actually i think i know why
I think its because to use the generalised mean value theorem in the proof, the function need be continous on the entire interval
You sure? It says "f,g [...] are continuous on the open interval. So we can use the generalised mean value theorem..."
The open interval doesn't include a
Tbh I don't quite understand the proof
if you're just checking your proof, there are plenty of proofs online to check against
I don't know if V is usual notation for what I assume to be a neighborhood; you might want to define it
Also the formula before the proof is missing an implies symbol
Yeah theres not much standard notation for neighbourhoods, my book uses V but ive seen N and B before
If I understand your proof correctly, it looks ok; but I'm not the best to ask
I'd follow riemann's advice
Okay
I always have troubke verifying my proofs; im yet to find somewhere suitable or somebody to help
Do you have any advice
No... I think verifying things is boring to most people, never mind proofs
And again I'm not the best to ask, sorry
It could be the case that some helpers would be willing and confident to review your proofs but they haven't stumbled upon your channels, idk
This is not a paid service after all
You might have more luck asking a professor in your university (or any nearby one if you aren't in uni)
@foggy sandal Has your question been resolved?
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i'm really confused on how to solve this problem. i'd assume they're asking for a 95% confidence interval, so i tried plugging it in to the formula, but how am i supposed to calculate a confidence interval w/ out the sample size (n)?
We don't really have context, but I guess the problem wants you to assume that the maintenance costs follow an approximately normal distribution. In this case, recall that, if $X \sim N(\mu, \sigma^2)$, then $\mathbb{P}(\mu - 2\sigma \leq X \leq \mu + 2\sigma) \approx 0.95$.
ucheo
One message removed from a suspended account.
soooo
do i plug in the values of my mean and standard dev. into the second part of that
to end up with an inequality?
would that inequality be the interval?
One message removed from a suspended account.
sry, im not actually taking stats rn, i have no idea what this means 😭
Yes! If a random variable follows a normal distribution, then the probability of its value being within 2 std. deviations of the mean is approximately 95%
show all your steps
,calc 3200-2*246
Result:
2708
,calc 3200+2*246
Result:
3692
sounds right
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What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
Around 2
Show your work, and if possible, explain where you are stuck.
Idk where to go from here in calculating the tension
Ooo a statics question
Complete the angles in the triangle
Wait why are you multiplying 200 by 9.8
it weights 200N you are already given the force
notice the unit
so can you find out T3
Do you know how to relate the angles and the sides?
Is it just the same?
show why is it the same if they are same
Not really lol
Hmm
Start with T3, what do you think T3 equals?
Because the direction is the same ?
I'm kinda clueless
Is it 200 N ?
Yep
Now let’s consider the forces acting on the intersection between the 3 lines
What can you say about the forces acting in this point?
Is the net force 0 because it's still?
Yeah
But we need to get clear what exactly is experiencing 0 net force
The system as a whole?
I'm not completely sure tbh
Hmm...what connects T1, T2, and T3?
Cables ? 😭
Well they are cables
But what location makes T1 and T2 and T3 intersect?
In the diagram
the beginning of T3 ?
Exactly
Now we know the system as a whole doesn't move
But this point is important because it allows us to find the forces in T2 and T1
so that means T1 + T2 = -T3 right
Not quite
Now do you remember the 2 equations of statics for stationary points?
Hint: it's related to the x and y directions
fnetx = 0 and fnety = 0 ?
Yep yep
Now we need forces in these directions to make use of these 2 equations
But it appears that T2 and T1 are not in full x or y directions
do we take the sin and cos of each of them and find the direction with the pythagorean theorem
of each one individually I mean
and since T1 is in the fourth quadrant it would be sin319 and cos319 ?
Wait
No no it's not in the 4th quadrant when you inspect it from the point you highlighted
Oh it would be the second then
Ye
Okay but how exactly do I find the tension in the cable from that
By using these equations
You found the x and y components for T1 and T2?
is it just the sin and cos of the angles relative to the point ?
Ye
Yeah but don't forget that they're not only the sin and cos.
The sin and cos must be multiplied by a magnitude
Namely T1 and T2 themselves
T1x = T1 cos(131)
Wait
139
T1x = T1 cos(139)
T1y = T1 sin(139)
why 139
180-41
Sadly that is not correct
thank you for your patience btw
We're happy to help :)
Okay and how do I connect this to the tension in each of the cables

I'll let you know if I need any more help (assuming you're not busy)
If you need any help, the help channels are open
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wondering if anyone can help

