#help-13
1 messages · Page 155 of 1
no prob :)
Closed by @elfin otter
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
how do I come up with this polynomial?
i know one of the zeros is (x+4)
but the 1+2i is tripping me up
isn't there like a conjugate your supposed to do for that?
one of the factors is (x+4).
sure is, because the polynomial has real coefficients.
since you know 1 + 2i is a root, you know that what other complex number is a root?
why 2+i and 2-i
oh
those arent the same numbers that you want as roots
mt
god
thats the mistake i made
god i can't read
or replicate
lol
so it would be (x-(1+2i)*(x-(1-2i)
?
Closed by @obsidian umbra
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Can someone check both of these?
thank you but what about first
,calc 240+1080
Result:
1320
well
why
,calc 240+360
Result:
600
,calc 600+360
Result:
960
,calc 960+360
Result:
1320
only one that fits
yeah
oh u have to check all of them
I just went right to 1080 because I know that number from skateboarding
Closed by @celest heath
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Lets start with T1
What does it mean to be in Kernel of T1
I.e. what is true about elements of the kernel
@covert island Has your question been resolved?
sorry! i didnt see this till now. we know that the Kernel of T is the set of all zeros of the transofrmation
right
so
So to define and describe them we start by saying that kernel elements are
v in Rn
But it's not just any v
It's only certain v that adhere to particular conditions
Now this is where you say
Well
They should be v so that
Tv = 0k
im sorry my brain is like stapled to kernel = null space = to 0 vector
cuz i think thats what the professor was getting at
Yes they are the same thing
Basically
To define the first
We'd say
{ v in Rn | T1v = 0k }
I.e.
Vectors from Rn such that when T1 is applied to them you get the Zero Vector in Rk
That would be the definiton of the kernel of T1
mhm
let me just process rq lol
so the general equation rn is T(v) = 0 vector
for k
correct?
If youre part of the kernel, then that should be true
right ok
So that goes on the right side of the set as the restriction
But first you have to identify what kind of objects are even entering T1
Thats the left side of the set
Its vectors v from Rn
Not just any old thing
mhm
{ Objects of this type | that follow these conditions }
Thats how you define sets with set notation
You can also sometimes describe it in sentences depending on your class/prof
i think he wants it as a sentence
so then the definition of the kernel of T1 would be T1 * V = 0vector?
The definition requires two things:
Mention where the v is coming from
Mention what should be true about the v
So first you must say that
v is a vector from Rn
ohhh i get it i think so then
The kernel is:
The set of all v in Rn such that T1v = 0k
can you explain the k please?
Thats the sentence version of the definition
Yes
When you transform
Sometimes you go to another space
In this case T1 is defined
Rn -> Rk
Members of the kernel start in Rn
mhm
That carries the Rn vector
To a different location in Rk
So when you say T1v = 0
That 0 is AFTER transformation
So the 0 vector is not the one from Rn
It's the one from Rk
Each space has its own 0 vector
So you specify which one you reach
this should be 0 vector k
right?
The 0 vector from Rk
Which your prof provided a notation for
I actually always just wrote 0 for zero vector it was never required of me to differetiate which one
ah ok
so then i have ker(t1) is t1 * v = 0k where v is a vector from Rn going to rk
or
no going to rk
is it important that i include that part?
Ker t1 is a set of vectors
Its not the equation
Its the vectors that go into it
So ker t1 is
All v in Rn so that T1v = 0k
cool lemme just process
Follow that structure
-
Define element
-
Explain restriction
ok so the defining the element part is here
.
and the restriction part is the linear transformation from n -> k
sorry if im a little slow btw, this is really hard for me
;-;
Let me rephrase this slightly
There is a 3 tier approach
- Identify what you are trying to define. In this case I am trying to define Kernel
Kernel is, ultimately, a set of many vectors.
- Once you know you are defining a set, you follow this procedure:
a. Begin by identifying where elements from this set originate from.
Once you do this, begin by introducing elements of the set.
In your case, Kernel is a collection of vectors. I need to specify what kind of vectors if possible. Because I know kernel includes input vectors, I can start by giving a broad description of elements of Kernel.
- The Kernel is the set of all vectors v in Rn.....
Thats the first half of defining the set
right so we defined kernel to be a set of many vectors within a domain that result in the codomain -> 0
the element of T1 originates in r^n
Ok now that i know where to start we proceed...
b. I need to provide some kind of condition or restriction to clarify who is or isnt part of my set.
The restriction in this case is that they must abide by the definition of Kernel.
Therefore, these v must follow this restriction....
.... T1v = 0k
and we can say this
You glue the two halves together to define the set
ok so i actually have a question about that
for this to be true
doesnt t1 have to be a matrix
All linear transformations have a matrix representation
Basically no not exactly but technically theyre all matrices sort of
Linear transformation can be defined without a matrix in some vector spaces and then you can make a matrix that fits the same transformation
For any possible linear transformation
For that reason the topics of Linear Transformation and Range/Kernel of Transformations is very closely linked to Null Space and Column Space of a Matrix
The kernel any linear Transformation is linked to the null space of some equivalent matrix representation of that same Transformation
ok cool
so all of this makes sense now
but
what about the T1 by T2 part
because that would be the dot product of 2 matrixes right
or is it the funciton of t1 with aspects to t2
Its basically
Composition
Do T1 and then apply T2
So where do things start in this transformation
Well if T1 is first
Then they came from Rn
So T1v happens
v rides to a new destination in Rk
So now v has become u in Rk
At this point you apply T2
ok cool so lemme apply it
so we start in vector N
What should be true about things in the kernel
Sure they are vectors from Rn
mhm
But ones that are in the kernel.of a transformation
So you describe it in terms of the transformation
What should be true about
T2 ° T1(v)
uhhhh im a little mega lost rn
So
T2 ° T1
Means do 2 linear transformations back to back
But actuallu
That whole process is itself also a linear transformation
right
So if im in kernel of T2 ° T1
so the first transformation would be t1
but what would t1's transformation be
??
It means that
T2°T1(v) = 0
It doesnt matter what happens in between
T1 sends everybody to an intermediate vector from Rk
But the final destination is what matters for kernel
The final destination is Rm
So regardless of what T1 did, once I apply T2 you get Zero
So you answer like this
Ker(T2°T1) :=
Set of all v in Rn such that T2°T1(v) = 0m
For a composition youre describing where you start and where you end, just like a regular single transformation
All the in between does not matter for the definition i dont care what happened when T1 was applied
Only what happens after T2 finishes
Its T2°T1
Think of that thing as one piece
Another way of writing it ks
T2(T1(v))
right
T1(v) may be non zero
But then T2 of that is zero
huh
but we said the def of ker(t1) is t1*v = 0
t1 v = 0 is the transformation right
This is actually like a completely different transformation
Imagine it's T3
T3 starts in Rn and ends in Rm
true
Yes theres stuff in between but i dont care about T1v = 0
Only the final T3v =0
right
so what im geting is this
T2(T1(v)) = 0
because no matter what the in between steps are
the final step will always be 0m
?
Yesssss
It doesnt matter if we hit 0 on the way or at the end
As long as at the end the final answer in Rm is Zero
Yes
so how do we tell which 2 subspaces belong with eachother
Although youd probably just call them vector spaces outright
hmmmmmm
Basically
ok cool
R1, R2,....
Rn
These are all different universes
They are the "parent" vector space usually
Subspaces would be things inside each of these universes
Yes
ill take that
They have different dimensions
true
You can create a mini R3 equivalent subspace in R4
But R3 vector has 3 components
And R4 vector has 4
They are not the same class of object
So things from R3 could never be part of R4
so r^n has n components
Yes exactly
Yes
Yes its irrelevant to the question
They could all be equal
We don't know which is greater or less than the others either
The only order we get is from the way T1 and T2 are defined
You can do T2(T1(v))
But can you do T1(T2(v))?
why can we do t2(t1(v)) if we dont have the dimensions
?
t2 sends us to r^m
Ok
So if i do T1(T2(v))
Im going to try plugging in an Rm vector into T1
Does T1 accept Rm vectors as inputs?
So this is an undefined quantity
If we do the other way
T2 ( T1(v))
We get T1(v) is a vector in Rk
T2 DOES accept Rk vectors
So T2 [ T1(v) ] is defined
Thats why your problem asks you about that one and not T1°T2
I gotta run for a bit im sorry if I have created more questions than I have answered, but hopefully you did get some answers xD @covert island
Closed by @covert island
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
use $\int cf(x)\dd x=c\int f(x)\dd x$ and $\int x^{n}\dd x=\frac{x^{n+1}}{n+1}+C$ :)
XxMrFancyu2xX
okay ty ill give that a shot
i'm confused so 5/(sqrt(x) | dx but then converting it to x^ndx the 5/sqrtx is throwing me off how do i know what x and n are?
@surreal cave
so using the first property $\int cf(x)\dd x=c\int f(x)\dd x$ called ``linearity" let's us move the 5 outside the integral so we get $5\int\frac{1}{\sqrt{x}}\dd x$
XxMrFancyu2xX
ah
so 5 | x^.5 dx + c
oh
5 | x^1.5 / 1.5 + C ?
nvm got it now
5 | x^(.5) / (1/2) + C
which is 5| 2x^(.5) + C
so 10x^.5
@surreal cave is that right
.close
Closed by @wintry roost
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
hii
i have been on this for 30 mins
half a page of scarrtch paper
i give up
if you can please show work
I would start by dividing everything by 2
@wraith warren Has your question been resolved?
also there's always cramer's rule
there is no need to drag Cramer into this
substitution or elimination will both work fine
hm
you can use https://www.wolframalpha.com and i'll show the work
the step-by-step should be free as long as you keep pressing next step
@wraith warren Has your question been resolved?
Closed due to timeout
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Im so stuck
my work:
bigger screenshots, I basically did the same analysis on f'(x) and f''(x)
please help me I'm getting no where 😦
@fervent pike Has your question been resolved?
@fervent pike Has your question been resolved?
Closed by @fervent pike
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
hello everyone
calculus is fun
it helps to write out the first ~5 terms of the series explicitly
i always try to use LaTeX when asking or answering someone but i always fail in that XD
$\sum_{n=0}^\infty (n+1)c_{n+1} x^{n+1}$
Denascite
tysm
shouldnt it be like this
no
why is that
try that
i tried first 3 terms and they are all different
what are the first few terms
for the summation on the LHS the first few terms are $c_1,2c_2 x,3c_3 x^2$..., the first few terms of the summation on the RHS are $0,c_1 x^2,2c_2 x^3.$..
yes so right hand side is exactly x^2 * left hand side
calculus is fun
wait a sec i totally forgot the x^2 on the LHS
tysm i wasted your time by such a silly question
Closed by @dim tiger
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
for ii, is it even possible to get 3 points that satisfy the conditions
because if you take the derivative of y, you get only 2 solutions, 1 of which is (2,3)
Yes, each solution for each line L2 and L3. What's the issue ?
the issue is that I get x=0 & x=2
show your work
yeah.
This is wrong.
L2 and L3 are parallel to L1. Therefore slope of L2 and L3 will be same as ... ?
@random kelp
the slope will be the same as L1
Good.
thats what ive done though
Now, Since L2 and L3 are perpendicular to C, why are you equating them to derivative at those points.
Derivatives give slope of tangents. Not of perpendiculars.
because thats how you calculate the slope at a given point
you don’t want the slope at those points
you want the slope of the normal at those points
Yes. But that slope is of tangent at the point. Not of perpendiculars.
do you know m1m2 = -1?
I do..
what you’ve done is set y’ = m
this says
let the tangent line to y have slope m
but that’s not what you want
Why can they not be ?
do you recognize that mcmeny?
I understand
,w graph |x|
here tangent at x=1 is parallel to line y = x+1, which is normal to same curve at x=-0.5.
i see
so I need to locate the points on the graph that are equivalent to the slope -1/3 cuz thats the perpendicular point
Yes
Slope at those points is -1/3 basically.
so I gotta make 6x^2-12x+3=-1/3
Yes
why didnt i think of that
@random kelp Has your question been resolved?
Closed by @random kelp
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
$\int_0 ^{\frac{\pi}{2}} \frac{\sin 2x}{\cos^4 x + \sin^4 x} dx$
Bettim
the answer is pi/2
,w integrate (sin2x)/(cos^4x + sin^4x) from 0 to pi/2
missing /
Closed by @fair mortar
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
$\int_0 ^a \arcsin \sqrt{\frac{x}{a+x}} dx$
Bettim
whe are theta and dx in the same expression?
I was too lazy to replace, although I didn't integrate so it doesn't make any mistak?
let me check, just a moment
have you tried using polynomial substitution like t=tan => sin = 2t/1+t^2 cos = 1-t^2/1+t^2 ?
seems about right, though you techically have to change the limits first
I am asked to use x = atan²theta
Yes but now I'm struck
How to proceed
IBP
I see but no one stops you to do second substitution
Right
yea
sure
upper limit:- $a=atan^2(\theta) $ so $\theta$ is $\frac{\pi}{4}$ unless I'm mistaken
physicsrocks
Lol where answer
,w integrate (xtan(x)sec^2(x)) from 0 to 1
,w integrate (xtan(x)sec^2(x))
Wtf
yeah, when you IBP that's what you get $x\int(tan(x)sec^2(x)dx)-\int \frac{tan^2(x)}{2}dx$
physicsrocks
Howw
wdym
I got xtan²x/2 - tanx+x
There nothing before that
try again
,rotate
seems right, but I'm still unable to see how you got the $-\theta$
physicsrocks
Tan²x is sec²x - 1 no,?
yeah, my bad. Let me try integrating this manually. I'll get back to you in a minute
wdym, your original answer was right, how did you geta different answer?
My original answer wasn't right
I forgot the /2 for the second 2 terms inside the Paranthesis
nah, MSE says that your answer to ∫xtan(x)sec^2(x) is right
Math satck exchnage
From this pic , see last step, I'm wrong
ah, got it.
Closed by @fair mortar
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
.close
Closed by @tidal wasp
Use .reopen if this was a mistake.
Maybe try it another time
stop ddosing the texit bot they'll find you
can you crash the bot doing that?
Feel free to post your question in a new help channel.
No it automatically stops responding to you
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Determine all $x \in \mathbb R$ s.t. $(x-3)(x+5)(x+9)(x+15) > 3$.
How would you approach this?
(By the way, there isn't really a pattern to the numbers here, I picked them randomly and would like to see how one would solve something like this generally)
By the way, there isn't really a pattern to the numbers here,
there's your problem
there's very little hope that this quartic you've got factors nicely
and I'd like to add to Ann and say that there's nothing that can be generalized here
no, one can extract from this the general idea that kepe wants to learn how to solve polynomial inequalities.
Oh. So for $(x - a_1)(x - a_2)\dots(x-a_n) > k$, you can't generalize some procedure?
To determine the set that x can be in
not unless $(x-a_1) \dots (x-a_n) - k$ has a nice factorization you can't.
Ann
Alright, thanks
if the roots are arbitrarily chosen as Kepe did, then there isn't a way to solve this generally, is what I meant
Hm, though if we have something like (x + 1)(x + 3)(x + 5) > 3, we know that the LHS -> infty for x -> infinity and to -infty for x -> -infty, so we just need to find the smallest x that satisfies the equality ... = 3 and our solution set will be (x, infty)
no, that interval will only be a subset of our solution set
x, infty, sry
unless you can produce proof that (x+1)(x+3)(x+5) = 3 has only one root
which i am not sure it does
Closed by @sand cradle
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Hey guys I have a question relating to probability and static.
If I was to have a book with 500 pages, how would I count how many letter of "A" are inside the book?
I had a rough idea of how it would be such as dividing the pages from "a", doing 500 divide by 1/26, would this be correct?
Cause there was 26 letters in the alphabet I thought it would be 1/26 or something
And use it to divide to 500
How would you approach this?
Or is it simple as just 500/26?
no
firstly the letters aren't evenly distributed
some letters are more common than others
as for
500/26
are you implying that on averageaappears once every 26 pages?
Nope
because that's essentially what that calculates
Hmmm
a basic approach would be to count the number of a in one page
and multiply that by 500
and that'll give a decent estimate
Hmm okay
CAuse I don't want to use a sample
Since it was incorrect way of doing it according to my senior
well then you'll need access to some external data
I was told to do what the question is requesting for
about how often a is used compared to other letters
No clue
size of the page / number of words that could fit would also be relevant
depends on the exact wording of the question and what is expected
are you expected to reach a numerical amount or
just the approach to how to obtain a reasonable estimate
you'll still need a bit more info
some sort of sampling would be required
i have a cabinet with several draws filled with fruit
how would you expect to know how many oranges i have knowing nothing about the cabinet
like there's
But would it be accurate if I just whip out any book to do it
?
but that's based off another sample
some books have bigger pages than others
and probably more letters etc?
i suppose you could estimate the number of words on a page
by multiplying words/line by number of lines
multiply
You don't divide at all?
OHHH
Right
So let's say in those 500 pages there is roughly idk 2500 letters in each page
So it would be like 500 x 2500 x 8%?
Oh okay
Would you please show me how you would do it?
Was I on the right track for it or?
its pretty much all been outlined
you just need to put it together and not make typos
So it would be 500 x 8% = 40
wdym by it
you'd want words/page
i suppose you could estimate the number of words on a page
by multiplying words/line by number of lines
500pages/book * number of words/page
will give
number of words/book
So it would be 500 * 2500?
2500 is a bit high for number of words on a page
But just an example it would be something like that?
if there happened to be a book that has 2500 words on a page, sure
but to my knowledge there aren't any that come close to that
you will
but currently the focus is on having a more realistic number for words on a page
i suppose you could estimate the number of words on a page
by multiplying words/line by number of lines
Closed by @harsh sparrow
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
does anyone know how this question would acutally work?
I have gotten G(w) and I know b is pi
so i have subbed in G(w-b) but do i have to multiply it out after this?'
@drowsy hare Has your question been resolved?
@drowsy hare Has your question been resolved?
have you tried using $\sin(t) = \frac{e^{it} - e^{-it}}{2i}$?
Bungo
yeah i have but I can't tell if I am making a stupid mistake as the calcualtion is so long tho
are you able to paste the work you've done? screenshot or photo or whatever? i can take a look
(although i have to leave for an appointment in 7 minutes, so it might have to wait until I get back)
yeah sure but its long hahaha
This is everything with all the things I have tried along the way
ah yea, this is more than i have time to look at right now, but i'll check when i get back, and if you don't already have an answer i'll take a look then
yeah don't worry, its been hard so itll probably still be here later
@drowsy hare Has your question been resolved?
@drowsy hare Has your question been resolved?
@drowsy hare Has your question been resolved?
@drowsy hare Has your question been resolved?
.close
Closed by @drowsy hare
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
To solve this
I first did trial and error
and tested values of n => 0 and <0
and got 0 1 -1 and -2
when i added them
i got -2
but the answer is 12
however
if we look at the absolute value part
you might think that you need to kind the modulus of each integer then add
but the last part of the questions says nothing about modulus
How should I apply the absolute value thing to solve the question?
just solve the inequality
First pretend like you are solving for |N - 3| in the inequality rather than for N
Meaning you get it to the form a > |N - 3| > b for some numbers a and b
Then you simply consider the cases N >= 3 or N < 3
whhy
Well if you had an equation like e^(2x^2 + 8) - 1 = 0, you would start with isolating e^(x^2) because you then can use logarithms, similar thing here
(Hint: ||As the first step I would use the property x1 > x2 > x3 -> 1/x1 < 1/x2 < 1/x3 for positive x1, x2 and x3||)
What
15 > 30/|N - 3| > 6
So
1/15 < |N - 3|/30 < 1/6
Now you multiply each side by 30 and get 2 < |N - 3| < 5
Let us now consider the cases
The first case being N >= 3
What's |N - 3| equal to in that scenario?
Why not N >= 0
What's the definition of |x|?
x
Nooo, otherwise we wouldn't waste time to write the bars 😅
|x| = x if x ≥ 0, it is - x if x < 0
Pleasee what do i do with this information
So |N - 3| = N - 3 if N - 3 >= 0
The latter can be rewritten as N >= 3
That's why we are considering that case
ok
Whata next
Consider the two cases, N > 3 and N < 3
Can someone help with this one
And solve the inequalities given
If N >= 3, this becomes 2 < N - 3 < 5 and 5 < N < 8
Post it on another available room
sorry
Don't worry
Same thing for the other case, try considering N < 3 on your own now
=0
- |N - 3| >= 0 for all N anyway
- That's not an equation
It's not the answer. However by definition abs values are ≥ 0 always
If N - 3 >= 0, |N - 3| = ?
3
I hope you are able to prove it, directly from the definition
Why do you think it's 3?
No! Re-read the definition I gave you (and replace x with N-3)
I never said N - 3 = 0
Yes, so what's the answer to this question?
The definition says that if x >= 0, then |x| = x, right?
yes
Now try writing this exact sentence but replace x with N - 3
why are we finding the modulus of n-3
Because we have modulus of n - 3 in our problem and we need to get rid of it
You can, but it is not really necessary
|n-3 |= n-3
Anyway, if you were to use this rule on N - 3, you would get
"If N - 3 >= 0, then |N - 3| = N - 3", right?
Yes
Always?
So, if N - 3 >= 0, this inequality becomes 2 < N - 3 < 5
That's the first case that we are considering, yes
And from here you just add 3 to each side and get 5 < N < 8
Okay, so the solution in the first case is (5, 8)
Why
If N - 3 >= 0, then |N - 3| is the same as N - 3. Simiarly, the inequality 2 < |N - 3| < 5 is then the same as 2 < N - 3 < 5
Yes, that's the solution to the first case. Now we need to move onto the second case. Namely, we need to consider N - 3 < 0
What's |N - 3| equal to if N - 3 < 0?
Correct
1 < N <- 2
Yes
Let's now look at the integer solutions
What integer solutions does 5 < N < 8 have?
Can you think of any integers that are placed between 5 and 8?
6 7
0 -1
12
Wait
So first
Posting for reference
So we look at the inequality
And because we are looking for n-3 without the modulus sign
we need to apply the rules
that | n-3 | = n-3
When n-3 is more than zero
Yes
Then we imagine situation when
n-3 is positive
and remove modulus signs
then solve
we get the range
then we do that for when it is less than zero
then get range
We then get the integer values of n and sum them
That is right
But can you please expllain why they began the question like that
Like what exactly?
Closed by @subtle horizon
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
Hello- I've been stuck on this for quite some time.
this is the full problem
possibly relevant defn
!status
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'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
1
I mean
I don't know where to begin
I was thinking of opening it up and doing any many integrals
but that sounds like a headache >_>
you finished part a right?
@late finch Has your question been resolved?
do you mind showing me your proof?
we use the equality in part a to show the inequality in part b
@late finch Has your question been resolved?
(X,Y)->(e^x cosy, e^x sin y)
Jacobian determinant is always non zero therefore it's invertible or kernel is just the zero vector
But the map is periodic
So LHS 0 RHS non zero
Possible
Closed due to timeout
Use .reopen if this was a mistake.
.reopen
✅
There might not be a neat solution
@late finch Has your question been resolved?
@late finch Has your question been resolved?
So?
That's the first thing you should try
This problem is just an application of the definition of the norm
what do you mean?
Do this
Question please
part b
So I want to confirm
?
I'm doing
|| f(x) - f(y) || = || integral ( Jacobian . (b-a)dt) t || being parameter for line
then moving the norm inside and taking inequalities
is that right 0-o?
Closed by @late finch
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
hey there, i actually posted the question before but then i had to go so i couldnt get an answer. I am solving an old exam to prepare for my exam soon and there is a question for a multivariable function f(x,y) = (x^2)y + ((y+1)^2)(y+2). The sub-task I couldnt figure out is the part where it asks for me to find all singular points on the curve 0 = f(x,y) and classify them with the help of the hessian matrix as double point, cusp and hermit. I of course did some research on it but i couldnt find something and the script my prof provided doesnt explain it well. Thanks in advance.
first singular point are defined with Df(x,y)=0 so df/dx=0 and df/y=0
oh i already know that but thanks, i probably should've been more clear. I am more confused about the classifying part
for Hessian Matrix you calculate 3 terms d^2(f)/dx^2 (you already calculated df/dx), d^2(f)/dy^2 (you already calculated df/dy) and df/dxdy than you replace the 3 expressions with the coordinates of singular points and you write the matrix : 1st line (d^2(f)/dx^2 df/dxdy)
2nd line ( df/dxdy d^2(f)/dy^2 )
This is so helpful in optimization problems because you can use this matrix to find the convexity of f in this certain point
i see, after that how do i know if a singular point is one of the three categories?
lets consider H=1stline(r s) 2nd line(s t)
you calculate the determinant D
if D<0 we can't conclude
if D>0 we test r
r>0 so f is convex
if r<0 f is concave
oh i thought this method was being used to find local min/max or saddle points
i mean of course you can also figure out if its convex or concave but i didnt think we'd use it for the classification of singular points
if it is convex or concave in a point so it's a local min or max
my english is advanced but still not my first language and im not sure what hermit means in this context, I translated it from the file which is in german, which is my 2nd foreign language so could you shortly explain what that is exactly. Idk why doesnt any dictionary provide something for this context.
like is it an isolated-point or something idk
.close
Closed by @round raven
Use .reopen if this was a mistake.
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
why is it 0.52 - 0.24
Closed by @boreal trail
Use .reopen if this was a mistake.
nvm
Send your question here to claim the channel.
Remember:
• Ask your math question in a clear, concise manner.
• Show your work, and if possible, explain where you are stuck.
• After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!
Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.
is the 1 cm a third of the whole length or not?
Why should 1cm be a third of whole length?
does octagon work like this?
Not really
Nope
uhh
the smaller side is 1?
You can slightly alter that. The middle part is fine if you want to say the sides of the octagon are length 1, but then you have, with the triangle in the upper left, a hypotenuse that's the same width as the top side of the octagon.
i think
Hmm, not really
Then the two legs of the upper left triangle are the same length because of symmetry.
legs?
Yes, do you see the upper left triangle?
these?
Well, that's the upper right, but yes.
Those are the same size because a regular octagon is symmetrical.
So, use a variable for the length of one of the legs.
Then write it next to both legs.
then it tells you its 1
Then write 1 next to the hypotenuse.
This might help, same colour lengths are equal
No, the legs aren't 1. The hypotenuse, one of the sides of the octagon, is 1.
should it be like this?