#help-39
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thx, but I wanna talk on dm
just going to add one more thing.
people are wary of people insisting on talking only on dms as that correlates with suspicious behaviour
Iam sorry, but it is my persoal issues that's why...
if you need personal 1-on-1 help it might be better to work with your teacher or a classmate in person; you won't find people here willing to talk in dms
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to fid the intersetction points for x^2 = 10(y+20) and x^2/16 - y^2/64 = 1
10(y+20)/16 - y^2/64 = 1
multiply everything by 64
40y + 480 - y^2 = 64
?
-y^2 + 40y + 480 = 64
π€
Rearrange first equation.
Then let y1 = y2.
i did
what is 40 times 20?
(10y + 120)/16
why 20
$64 \cdot \frac{10(y + 20)}{16} = 4 \cdot 10(y + 20) = 40(y + 20) = 40y + 40 \cdot 20$
knief
no clue where 480 came from
ill do it 1 by 1
(10y+200)/16 - y^2/64 = 1
10y and 200 because there was 10 multiplying it
here
you did
multiply everything by 64 and for the fraction with 16 as the denominator divide it by 16
uhh
?
what
If you're multiplying trhough by 64
Then the fraction with denominator 16 becomes 4 times the numerator
yeah thats why u divide it by 16
thats what i did
No it's already divided by 16
what
this translates to $\frac{64 \cdot \frac{10(y + 20)}{16}}{16}$
knief
yh that's not "it", when you say this
"it" here refers to the fraction, not the 64 you're multiplying it by
forgot to specify just the numrtor
so when u do that it becomes -y^2 + 40y + 800 = 64
then u just do 800 -64
then quadratic equation
to find the intersection
alr thanks
π
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i need help solving some parametric equations, we did this at the start of the year and i have no idea how to solve if their paths meet/if they collide/if theyre parallel
x=2t+8 y=3t-4 z=9t+4, x=9t-6 y=t+4 z=3t-8
first off, to check if theyre parallel, look at the coefficients of t
well the coeffs are different for like the xs ys and zs across both so i assume not
nice
ok, to check if they intersect, they have to have the same x, y, and z value for some t for each
you have to separate the two t values, so pick a different variable for the second one
you now have 3 equations in 2 variables, if they are consistent, then they intersect
consistent meaning that after solving for t and u, the third equation should also work
yes
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i got
a>25 U a<-25
however answer is given a>25
my reasoning for a<-25 was that the 2nd term is always continous
so 1st term should be continous
for first term to be continous the gif part has to remain constant whole interval
the numerator lies between 1 and 25(both included)
if a>25 the gif becomes 0
if a<-25 then gif becomes -1
gif is greatest integer function or floor function
plz ping if you answering
Is that GIF become discontinuous if it have integer value?
yeah
gif becomes discontinous if at integers
lhs and rhs become different
lhl and rhl
left hand lmt and rt hand lmt
So i think if f to be continuous in [4,8] then i think either that GIF must not have inside value reach integers
or if it does, then the term multiplying it also a 0
indeed
the term multiplying cant be 0 for whole interval
so only was is for gif part to be const
but if check sin(x-3)=0, no x satisfies it to be 0
3*
in that given domain 4 8
oh in domain no
yeah so we cross this scenario then
because it is not sufficient for any x in that domain
yeah so what did you do to calculate in the other scenario
find range of the numerator
first you would need to substitute in x=4 and x=8 of the GIF to find the value of a that spans the domain
x=>[4,8]
x-3=>[1,5]
(x-3)^2=>[1,25]
nah u dont need to do that part
really?
the thing i did faster and easier
I thought intuitively i would start it first
so you consider two cases for GIF?
so you cant say it would be max at start
either is GIF is constant 0 or >=1
gif being constant is only way
it cant have multiple values
or else the function becomes discontinous
Ok so i just calculated out that [1/a, 25/a] spans the interval 4 8
But for GIF to output an only constant integer value across this span, there cannot be any integers sitting between 1/a and 25/a, right
indeed
so i think the constant value n either have 2 cases
0 or >= 1
whereas n here is an integer
where u getting the > sign
that GIF can get the output greater than 1, no?
But we are not sure, so we say, suppose GIF produce a constant integer n, then n <= 1/a <= 25/a <= n+1
so it is false there
lmao
but wait can you tell me again what did you do to solve so i can check where did you go of trail
find range of numerator
gif has to be const
a has to lie outside range of denominator (make it never become integer)
so a>25 or a<-25
ahh i see why
the question stated that f must be continuous on 4,8
then it must be left-continuous at the right endpoint right
this means if you approach x = 8 from left hand side then the limit is exactly f(8)
uhh then you can test by plugging in a = -25
then when x = 8, GIF = -1, but once you change x = 8.0001 (past 8), then GIF jumpt down suddenly
no you were right but you are just confusing on how that GIF handles limits at the boundaries
i put a>(-25) so boundry case becomes useless
I can only verify that if a negative value for a that satisfies the question exists, it must be < -25.
thanks
If it exists
ima go do more questions
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How do i do q3
Im thinking something like p(x,y)?
@dense storm Has your question been resolved?
<@&286206848099549185>
Ye
3
!nopdf
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!nosols
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
Why does f(1+yd) = f(1+y)
Am i not understanding an important part of functions
O wait
I read the wrong thing
Oop
Say cos(x+ycos(x)+ y = xy +cos(x+y) You'll understand then
!nosols
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
dude keep sending solutions
I said ""Say""
what?
I gave an example
They are not talking about what you said
They were replying to the image sent by Krish
What does f cannot constantly equal d mean
<@&268886789983436800> This guy is giving solutions
Yo what is this solution ππ
Or am i too dumb for this
You need to apply some critical thinking
yea
The one like !nosols
@dense storm Has your question been resolved?
We don't generally allow full solutions to be given to problems, and we are doubly unhappy when they're taken from AI 
You have a day to be timed out, which is [nicer than we need to be](#changelog message)
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hi so i guess the easiest way to start is by seeing what happens to L(b1) and L(b2) but what do i do after?
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mb
Whats your doubt
Hello, @sharp delta!
who pinged me
me
I asked is this a post jee re-lock in
lock in for uni now π₯
then why did u delete π
no i am trying my best to lock out rn, started netflix+discord+insta+roblox+minecraft+doomscrolling
π
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I got it wrong
Pls help
(In the future, please make the first message you send the actual question since that's what the bot pins. This saves us the effort of having to change the pin manually.)
vertex, not axis of symmetry. The axis of symmetry is simply the vertical line that "splits the graph in half", namely x=3
so you should have also drawn the line x=3 dotted in or something along those lines
Oh ok
that being said, this is the only real issue I see right now
is there something else that's giving you pause
I checked my answer according to my book and I got it wrong
Shield I show the answer
Wait nvm
I looked at the wrong page again
rip
Iβm so sorry
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β Original question: #help-39 message
Can u help me w this too.
Do I use my original question for y or my new one
Can you provide the exact context?
This one
Question 4
No I mean 18
The working out is correct for the turning point if that is what you are asking.
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It's kindda funny
Next time dont do trolling like that ig
Ngl
@hoary relic whats ur major
Alr
Advanced maths
(You know undergrad is self selectable right)
I solve olympiad question in eating time
(I chose that role so i can access advanced channels)
Hey can you help me?
I have olympiad exam in 3 months
Ioqm
Give me tips
It's my first ime
i forgot about this discord server till i got to modern physics
What should I focus on more
but ima just ai my way through it
Number theory
Algebra
Comvinatrics
Or geometry
In which should I focus more to qualify
gemini guided learning isnt that bad too
Any more tips
and their notebook in gemini
Hmm I'm still in 9th grade so no unfortunately
You're indian
So
You eman
Mean
I
Solve my problems from gemini
Right?
lowkey
Why
u dont have to just copy down the answer looking at the steps can help
In js 3 months π
Any books?
Is book required ?
u can just find the textbook on some pdf
on gemini u can upload the textbook and like use that
Wooow
or walk into a random lecture to ur nearest uni
I'm a school student
I'm in high school
take calc its in bascially everything
Alr alr
Whats ap?
are you american
nah
ngl ur tweets are kinda crazy
Wdym π
@pliant stone Has your question been resolved?
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The figure shows the graph of the function
y = A sin kx + B
Determine the constants A, B, and k.
So you're missing the value of k?
Yuh
try tracing this perfectly straight blue line here
Did you try getting it?
notice anything?
I am taught that in order to get k, you take the distance between 2 tops
Right
The problem there is that the tops are a bit off of a clear value
Then I suggest getting the distance from the axis of propagation (the line that B corresponds to)
Like what MarcoMa210 was indicating to
I don't understand π
Yuh
so we know the y value is at -1 when x is 0
and so we grab the next x value where y = -1
it's this green line here
Is the answer 45 * 2.5 ?
and why would it be that?
no if you're thinking like that then it's 30Β° * 1.5
because you add half a grid space
Hmm
This shit is so hard π
Do you know the period of regular sin(x)
180 ?
Yeah
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is there a smart way to do this using determinant properties or do i need to expand every one and show?
Which question?
any
For Q2) you can subtract rows, and that will keep the determinant the same.
yeah it worked
oh i think i can do the same in 04
so gonna be x, y and z in the diagonal
and 0 in the rest
So all you have left is question 3 right
yes
ok
recall that multiplying a row or a column by x makes the determinant multiply by x
yea
in the first determinant, you can spot some a and a^2, while in the second, you can spot some a^2 and a^3
can you spot how we could manipulate the first to look more like the other?
hmmm i think i can take the tranpose of the first and then multiply the first row by a, second by b, and so on and then the thid column gonna be abc for every one
so i can take off
but idk
we can do that yeah
just remember that everytime you multiply a column/row by a number, you gotta compensate back in the determinant
so $\begin{vmatrix}a&b\c&d\end{vmatrix} = \frac 1x\begin{vmatrix}ax&b\cx&d\end{vmatrix}$
Rafibirthday2003
(provided x isn't 0)
yeah this works
and then we can exchange columns 2 times
and the sign gonna be the same
exactly
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now there is a slight hiccup just in case a,b or c is 0 (because in that case what we did isn't valid)
you just have to check that it still works in those cases
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guys can anyone help me with group theory?
!da2a
Asking the actual question right away is more likely to get responses.
Asking "Can I ask...?" or "Does anyone know about...?" doesn't give people enough information to decide whether they can help, and answering can feel like a promise to help with the actual question, which they might find themselves unable to.
why NOT
Not recommended, since they might be wrong and no one else would be there if it were to be in dms. Its best that you post the question here
Also like why would you not want to post the question here
because its not really a question is more like idk whats going on in the topic
its about orbits and stablisers
In that case you could go to #groups-rings-fields or #advanced-algebra
If you cant chat in there , read #get-advanced-access
@lusty gull Has your question been resolved?
You can always just point out stuff youβre having trouble understanding
@lusty gull Has your question been resolved?
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let $P$ be a point inside triangle $ABC$ such that $\angle BPC = 180 - \angle A$. Let the reflections of $P$ across $BC,AC,AB$ be $A'$, $B'$,$C'$ respectively. Show that $A',B',C',A$ are cyclic
Copter
well clearly A' lies on (ABC), and by equal sides we know BC'A' is isosceles and similarly for other triangles
is that sufficient to just angle chase?
guys i suck at geometry pls help
Ooo so tbis is one of the easier ones that I can help you with
Yes it should be an isosceles
yayπ₯Ί
yes it should be
I think the angle at A should be half of angle C'AB'
Oh but also
Look at P's pedal triangle into D, E and F
Its the same as that of A'B'C' up to a scaling factor
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Is it possible to give a translation?
D is a dedekind cut so D is a decreasing set
D doesn't have a maximum
ah I see what prof means now
suppose d in D, with D being decreasing set
now suppose c < d
if c < d then since D is decreasing set then c in D which is absurd
comments such as these are unnecessary and unhelpful
@stoic imp Has your question been resolved?
@stoic imp Has your question been resolved?
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On an 8Γ4 chessboard, a king is placed at the bottom-left corner π΄. The king can move one square at a time in any of the possible directions.
How many distinct paths are there for the king to reach the bottom-right corner B in exactly 7 moves?
to get from column 1 to column 8, the king has to move exactly 7 squares to the right.
since the king only has 7 moves total to reach the destination, what does that tell us about the direction of every single move he makes horizontally?
Think it might be 8 tall
see the image
the king can move in any direction
Diagonal too right?
ofcourse it can't move straight up
Basically the king
yup
Always has to move horizontally
At any time
Whether it is diagonally or straight horizontal
yes
So how many options does the king have at any point in time?
Say the first move. To which squares can the king move?
either the diagonal one or the adjacent horizontal one
So for every point in time, the king has 2
Except
At a certain time
I min
Ill show the diagr
let's get this step by step the king starts at the bottomleft corner which is row 1, every single move must take him one column to the right
so his very first move, what are the only rows he can land on?
If the kign is there...
Np
that point is the topmost point it could get
Also
Ill mark the places
Where the king has only one legal move
I think this is self explanatory
crct
are you crazy
i have an idea-
hm
in some squares the king has 3 choices
-# 3 possible paths
and this is true for all of this squares in row 2
now for the bottom row each square only has 2 choices continue forward or go up-
and for the top row u can only touch it- once or twice per path
crct
at 2 squares
now
?
well we will first calculaute how many posibble path for the first row
then second row then thid row and so on-
this is my idea atleast there is probably a more optimail way to do it
basically the idea here is that u count once (the bottom path) and then u multiply how much options u have at each point
but in the last 2 rows, we can also make zigzag motion and it can move diagonally. so practically it will be very difficult to count all the possible paths
we are bassicly calculating each postion what possibe otipons exsist for it-
so that is accounted for because we will also be counting those paths in te 2nd row that lead back to the first row
if we repeat a "winning" method for each layer of squares we produce an image like this
I have an idea
each path is legal, since we always advance 1 square
Since if you go up you must come down the same amount
so we make an "arc" of solutions
thus, how many unique solutions arise from this set?
-# thank you btw
(that graph is nice)
-# no problem, ill step away for now to let you continue. Figured i'd contribute my understanding of it, perhaps it finds itself helpful
-# no no feel free to take over i am really lost π or if ur busy atleat stay and watch over incase i say smthin wrong
this can be done algeberically through a fucntion maybe?
-# ill be going for dinner in a lil bit, but ill watch over for now
You could think of a move as moving horizontal up or down
I'd argue: see how many paths each "layer" has (since each layer is a new set of solutions, and there should be a function which can describe this [im thinking combinatorics rn])
And find combinations for it
true true that is another path for a solution
But I have no idea how to ensure that an up move always comes before a down move
-# well its onyl true for row 1
-# Wdm?
on other rows u can go up or down it doesnt matter (atleast except for the top row)
Well no im treating the problem as a whole. If you move up 2 times, you HAVE to move down 2 times
-# this is true (i.e. it follows my above sketch)
But after that im stuck. I know how to get a combination between moving horizontal, up and down, but i dont knwo how to ensure up happens before down
imo, easiest way would just be brute force
probs less time consuming than finding an actual formula for it
but you can find a "rule" instead of a function
at step N, I have X moves I can make, thus for some path K on step N, I have X solutions
where each path K, is 1 layer higher than the previous
from there its number crunching, so I see brute force being easiest approach
After googling its related to a Dyck (yes thats the name) or a Ballot sequence
@loud wraith do you know what they are?
what
at step N, for K>1, where K=1 is the starting case (ground layer if that makes sense). We have 3 moves for every subsequential step N+1, however at some point we must make 3 moves (down, right, down-right) and then 2 moves (right, down-right)
that should be the # of paths for each layer K
total permutations are too much
for the first and second row, total number of choices will be 7!/2
no wait
U cld try this. But I have no idea what it is unfortunately
-# ^ ^ with some added help from knowing how many possible moves can be made at each step
leave it guys
y r just telling your views on the question instead of solving it
didnt even analyzed the problem properly. you cant just take any move straight up.
.close
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I think when they said "up" they really meant diagonally up
You did establish earlier that you can't move straight up
"up" would fail the problem in every case, since min(moves) will always be 8
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The asker has left, but this is actually an interesting combinatorics question.
My idea is to break apart this problem into four cases: 0 diagonal movements, 2 diagonal movements ... 6 diagonal movements. The first case is trivial, just 1 possible scenario. The second case is also straight forward:
We are essentially arranging RRRRRDD, where R means to go right, and D means to move diagonally. The first diagonal has to go up, the second diagonal has to go down. So that is 7!/(5! * 2!) different cases.
The 4 and 6 diagonal cases are a little more interesting. It is interesting because you can have both up diagonals first, or you can have one up diagonal and one diagonal. In that case, you need to consider further casework and find the number of ways to arrange DDDD properly. You find that there is only two possible cases; UUdd, UdUd (where U = up and d = down). The constraint is that you cannot move down more times than you have moved up, which makes sense based on the scenario. That means you have a few constraints:
- The very first diagonal must be up always
- The next two diagonals must not be down
That means you multiply 7!/(3! * 4!) by 2.
For the 6 diagonal case, you can apply a similar set of logic;
- The very first diagonal must be up always
- The next three diagonals must not be down
- The next two diagonals must not be down
(On inspection, I think this diagonal case is also a little tricky than just the above cases, but can still be managed if you brute force it)
Then from here, you just add all the cases up. I think my reasoning covers everything.
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-# pretty neat solution nice ;3
It is pretty bashy but I mean you sort of expect as such with a scenario that has a lot of free movements and hidden constraints
But yeah thanks π There might be a way to refine it and/or look at it in a different perspective
-# if I may add, if one is interested in problems of this nature, one may look up what Motzkin paths are!
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i need help with this
my teacher says that the miles are the radius but i dont know how to measure that out on a graph
Wdym measure
Oh like
You're not sure how to draw a circle of radius 7?
likee if the miles was 7, then the radius would be 7 units but i dont know how to do the 7 units
OH WAIT
i think so
Wait
i could just add 7 to 2.5?
So you do know how to draw a circle of radius 7
Yep
That'd give you a point on the circle π
9.5 is a number, what might be the actual point?
Excellente π
i meant (2.5, 9.5)?
Yep. I had an idea you knew, but just to double check
i think maybe i would say (4.5, 3) is the epicenter?
Yeahhh so the funny thing about this question is that all three graphs seemingly don't intersect, which is very interesting.
I'd say you are roughly right π
i dont know how specific my teacher would want it though
You could find the centroid of these three points and call that the epicenter
wait I just realised
(-4.5, 2.9) is more accurate πββοΈ
I don't know what this is but I'm going to trust your graph is fine π
wait and then for the last part about the earthquake⦠am i supposed to make a circle with a radius of 10 around the epicenter we just found?
i said yes for it
yep
i dont know what to explain π
Oh well
I mean you said it yourself;
You should start by drawing the circle with radius 10
Then consider if you were standing at the point (4, -6)
i dont know how to explain the answer
Welll
I guess
What if you answer the question straight up?
As in,
Do you think you'd feel something from the earthquake at that point?
the epicenter is the origin of the earthquake which extends 10 miles outβ¦ THAT MEANS to draw a circle with a radius of 10 around the epicenter (approximately -4.5, 2.9) by doing so, youβll find that a person standing at (-4, -6) does feel the earthquake πββοΈ
Good.... why?
Why does the person feel the earthquake?
becauseeeeee theyre standing in the earthquake 10 miles big circle
Perfect
π i think i said that already OH OKAY
The person is standing inside of the circle, hence they feel the earthquake
I was being picky because you didn't explicitly say so :)
Teachers are usually not this picky... hopefully
mine isnt but this is on my test tomorrow
can i have more help?
i got this question originally wrong for having a poor explanation
i need lots of help with explaining things
All goods! Well, explain it to me how you normally would first :)
i said βthe point wouldnβt be in the circle because just by looking, 8 goes beyond 5β i can see why i got it wrong
Hmmmm okay, well why did you get it wrong?
Do you know why this specific reason is not quite right
I.e do you know the actual answer to this question?
Oof okay
I was sort of expecting a specific reason π
But no worries, I'll go through it with you
The specific reason why your reason is wrong is because it doesn't actually mention the properties of a circle
oh yes
To determine whether a point is on or off a circle, you really need to actually mention the circle in some way
So, maybe start with that :)
As in, what's the circle here?
and i was also supposed to like simplify the square root of 39 and 17 as in like turn them into whole numbers rounded to the nearest tenth?
π
A circle has two key components; what are they?
its round and has infinite amount of sides
???
Okay yes, that is true
Is there another important two properties of circles?
Maybe something a little simpler
Theres two things that every circle has that is very very important
Good! Okay the circle has a center, perfect.
circumference
What else?
points?
radius diameter!!!
But this thing is more important
Perfect!
So a circle has two things:
A radius, and a center
Now, based on this question
Can you figure out what the radius and center of this circle is?
i dont think it specifically says how big the circle is
cause 8 can be in the circle and so can 5?
have you done the equation of a circle
well the center is given: at the origin
whats that???
its a way to graph a circle x^2 +y^2=r^2
OHHHHHHHHHH
i think thats learned later for you
nuh uh
ill let the other dude explain i think hes better than me
that was on the test
ah
πββοΈ so i should plug in the points
@humble root i know how to prove if a line is a tangent to a circle, but how do u prove if a point is on a circle?
yes
i think
and work out the radius based on the first given point
Hint: ||As you say, x^2 + y^2 = r^2
If the point isn't on this circle, I wonder what happens to this equation?||
I gotta go soon anyway, did you want to explain?
@sharp sequoia do you understand?
im alright we just had a test on this lol
Oh lmao
π
me too!
Anyways, as David said:
You might remember that
The radius is the distance from the center to any point on the circle.
How then might you find the radius of the circle?
Alright, try it :)
u have to find the radius too
Tell me what you get
What is the distance formula?
do you remember?
square root of⦠(x2-x1)^2 + (y2-y1)^2
Perfect!
WHat's (x1, y1)? What's (x2, y2)?
Wait the radius is 8? I don't think so
wait
nvm I can't add things
Yeah
The radius is 8
You can figure this out by using the distance formula, and substituting the points here
i just removed 0 because it wasnt needed so 5 squared is 25 and then square root of 39 becomes 39 when squared
Yep.
because then ill find the radius of 8 sqrt 17
(8, sqrt(17)) yes
ITS NINE
Uhuh and what does that imply?
its not on the circle
and i can explain the process in a bunch of words
of finding the answer i mean
Why?
because its radius is bigger than 8 meaning its beyond the circleβs circumference
ummmmmmmm
π
Good!
I'd describe it like this:
The radius of the circle is 8, but the distance of the point (8, sqrt(17)) is 9. That means the point lies outside of the circle.
Alternatively, the rightmost endpoint of the circle is (8, 0). That means (8, sqrt(17)) is definitely further than the circle, since you are just then going up from the endpoint.
However, the most important point is - when you have a question referencing circles, you should probably bring up the actual circle!
The best strategy to answer any question is to actually deal with the specified thing in the question, whether it be a circle, or any other graph.
Anyways, I gtg now. Hopefully that answered your question π
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how do we solve this?
Show your work, and if possible, explain where you are stuck.
I havnt attempted because i dont know what the question is asking
So what part of the question do you not understand?
The key idea of the question is calculate the area under the curve
i.e. area under g(x)
basically this
actually only this
and calculating the upper sum
@desert cliff Has your question been resolved?
you're making a subdivision of the interval [7,8]
So, as suggested, you're going to split [7,8] over intervals [7, 7 + 1/n], [7 + 1/n, 7 + 2/n], ....
the k is just to quickly indicate how the points of the subdivision are defined
k will take any value between 0 and n, exactly as written to the right of the brackets
so we can have k = 0
that gives the subdivision point 7 + 0/n = 7
we can have k = n
that gives the subdivision point 7 + n/n = 8
and any value of k in between
so 7+ 1/n for k = 1
7 + 2/n for k = 2
etc...
We very often use "k = 0 to n" instead of the writing on the right so we can compress neatly what we want to say, instead of having to write down every single point with the "dot dot dot" writing
Like with summation
instead of writing $1^2 + 2^2 + 3^2 + ... + n^2$ to write that we're summing every square of integers between $1$ and $n$, we'll write
$$\sum_{k=1}^n k^2$$
Rafibirthday2003
ah that makes sense
that k=1 just means were starting from 1
but k takes on any values
and n is the last value
exactly
and k will take on every (integer) value between the starting and the ending value
ok, k takes on any value between 0 and n
meaning the subdivision is made of how many points (not intervals)?
I also guessed the width to be 1/n so I might need clarification on that too
Well I guess we can start with the width, either is fine
your choice
oh we can just start with this
im just tryingg to think
So, there are as many points as there are possible values of k, right?
If I ask you to count, let's say, from 0 to 5
How many integers would you count
n=6
yeah points and values of k is the same thing
number of integers you would count is 6
here I chose the "n", the end value, equal to 5
So in general, when I ask you to count from 0 to n
how many integers do you count
0, 1, 2...n?
yeah
how many integers did you list in total here
(accounting for the dot dot dot)
n+1 right
yes
so, our subdivision is made of n+1 points
How many subintervals would that make?
nah, it's the opposite
here we are at the classic fencepost problem
you said it that 0, 1, 2, 3, 4, 5 makes it 6 points in total
because i was counting the interval outside the end point
the interval [7,8]?
Doesn't count in the subinterval count
in any case, think of the subintervals as fences
every subinterval [a,b] must be delimited by their endpoints, the "fenceposts"
what are those two intervals on the edges doing?
The one on the left doesn't have a beginning point
and the one on the right doesn't have an endpoint
Back to this
thats true
an interval [a,b] always has a beginning point, a, and an endpoint, b
so it's the other way around
https://en.wikipedia.org/wiki/Off-by-one_error more onto this problem if you're interested
An off-by-one error or off-by-one bug (known by acronyms OBOE, OBOB, OBO, and OB1) is a logic error that involves a number that differs from its intended value by 1. An off-by-one error can sometimes appear in a mathematical context. It also often occurs in computer programming when a loop iterates one time too many or too few, usually caused by...
It's a common mistake
ok that makes sense
So n+1 points, n subintervals
ok
now we have n subintervals
their width should sum up to what?
(remember what the subintervals are a "sub" of)
sum up to the original interval
They should sum up to the width of [7,8], yes
Which is = ?
I assume partitions are another word for sub intervals
In this case yes, almost
Partition is another word for "subdivision"
"We partition [7,8] into intervals of the form ..."
Is the same as
"We divide [7,8] into intervals of the form..."
so partitions = subdivision = the black points?
Ehhh, the partition is more like the set of subintervals
A partition is a way of splitting up a set into different subsets such that :
- Everything that was in the original set is in one of the subsets
- No two subsets intersect each other
We often conflate subintervals and the points because one is exactly linked to the other
And it's easier to write {point1, point2, point3, ...} than {interval1, interval2, ...} because intervals are longer to write
I hope that was clear enough
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β Original question: #help-39 message
nth partition?
upper sum and lower sum
I didnt read the earlier context but from that image that seems to be the natural conclusion
I assume its just the points right?
so how do wwe calculate it?
Well you go back to the definition of your lower/upper riemann sums
@desert cliff Has your question been resolved?
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Solve x + |x| = 0
you should divide this ecuation into inecuations
Idk what that word means
yes, so the module of x is always positive
Yeah
so lets base ourselves on x>0 and x<0
try with x being a positive number
any positive number you want
You get x=x
3 + 3 = 0
which is untrue right?
Yh
now try a negative three
-3 + 3 =0

