#help-36
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Hello, I was wondering how I can do this question. Im confused because there are some boxes bigger then others and i wouldnt know what to put for some corners (we need to use pascals triangle)
treat the missing path as 0
For each point on the grid, count the number of paths from the top left to that point
Starting at the top left and moving down
so would i just add 0+ whatever the other number is?
yes
convince yourself this is valid with the simplest case
a single square with an edge removed
the idea is that it's 0 because the paths that COULD use it arent there anymore
so it's 0 paths from that point
okay but then what would i add for this do i just do 3+0?
yes
ohhh okay
wait
i meant that as in when you add the paths together the one coming from the missing path is 0
you should have a 1 above that 0
then 3 + 1 0 = 3
don't skip cells when theres a path missing
so i still put the 1 in between the two 1s up here
yes
when you add it to the corner below yea
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HELLO can someone pls help me w these two questions
idk how to do proof by induction with diffentation especially to an unknown order of a differential
the second question i only need to understand the first part then i’ll be fine with the rest
tell whoever wrote ts to learn latex
proof by induction is a method to prove things
edexcel exam board
it works the same as any other you've done
i don’t know how to apply it, let me show you how far i’ve gotten
pretty good handwriting
ok what do you need to do to get information on d^(k+1)y/dx^(k+1)
hint: d^(k+1)y/dx^(k+1) is the derivative of d^k y/dx^k
well firstly what i'd do is set (3^k+1)/2 and (3^k-1)/2 to something like A and B, so it's easier to understand.
then prove the case for n=k+1, which is just an application of the product rule
yes i got it thankyou :)
it’s coming together
i’m too autistic for that
how about Q 11 part a
but u seemed to have figured it out 👍
split the odd and even terms?
i’ll attempt
like for 2r, it's be even, and (-1)^even is 1, and same logic for odd
first year of university maybe?
@tight zenith Has your question been resolved?
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Would like help verifying if my proof is logically sound and rigorous.
Proof:
I define f(x) = cos(x) - x^3
Cos(x)andx^3 are continuous for all real x, thus continuity is satisfied
I choose interval [0, pi/2]
f(0) = 1 - 0, 1> 0
f(pi/2) = 0 - (pi/2)^3 = -pi^3/8, - pi^3/8 < 0
We get f(pi/2) < 0 < f(0), so L = 0 satisfies f(pi/2) < L < f(0)
By IVT, There exists some c in (0, pi/2) s.t. f(c) = 0.
cos(c) - c^3 = 0
let x = c
cos(x) - x^3 = 0
or cos(x) = x^3.
Thus there exists an x in Real Nums s.t. cos(x) = x^3
looks good
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can i sub a.b =2 in that 2axb thing
then (a.b.a) x b
(|a|^2)(bxb) ------> 0.
c vector = -3b na
b.c = -3b^2 (cosalpha)
dk if im right tho
No because it's wouldn't be a.b.a (which is not even defined) but (a.b)a (which is a vector.
Moreover, clearly 2axb is not always 0 so this couldn't have been true for all a and b
oh
ok ig got it
but how do i procceed now then
Since we want to calculate sin alpha it makes sense to do bxc
The sin being squared hints at the length of bxc maybe
@vapid haven Has your question been resolved?
@vapid haven Has your question been resolved?
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I’m having trouble with this integral. Is it cyclic?
yes
yeah it is, so a trick you can do is set I equal to the orginal integral
(also be careful how you write things
this looks like subtraction but you meant multiplication
)
Interesting 🤔. Is this one of those that gets manipulated algebraically?
Is this the correct integral that needs to be set equal to original?
if youve seen any cyclic integrals they will have been exactly like this one tbh
This is my first one on the homework. We did it in class briefly, but I didn’t understand it 100%.
oh youre asking whether your work so far is correct, i misinterpreted
Yes
hmm
why did we swap what parts u and v were taking
originally you had u = the exponential thing and v = the sine thing
then you swapped?
Oh I think that was an accident. I see. Second u is supposed to be the trig?
well like
i think you dropped a factor of 2
maybe -2
and your result will be that the integral is equal to itself
ah thats where the negative sign went
also if you want to make this mean multiplication you have to put parentheses around the second thing or else it means subtraction
good handwriting
Thanks, if only I could write the right stuff 💀
I’m going to retry. Brb.
Do I need to set this equal to orig?
I lost the 2* im adding it
-# this still means subtraction... youd have to parenthesise the second thing, that is: cos(2t) (-e^-t)
yes, that seems like a useful thing to do and its always allowed
Are u finished?
Correct
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$\lim n\to +\infty \frac{\sin{(\pi xn)}}{\pi x}$
Goofy Joe
How is this limit calculated?
!show
Show your work, and if possible, explain where you are stuck.
Sin oscillates therefore should not exist
This Is my work
,w $\lim n\to +\infty \frac{\sin{(\pi xn)}}{\pi x}$
Failed to get a response from Wolfram Alpha.
If the problem persists, please contact support.
That won't work here
Try thinking sin(theta)/theta= 1
$$-\frac{1}{\pi x} \le \frac{\sin(n \pi x)}{\pi x} \le \frac{1}{\pi x}$$
Ajay
Because the lower and upper bounds are different numbers, the theorem cannot conclude that the limit exists
How?
Squeeze theorem only works when lower and upper limits are the same
Yup
It does not work in this case
Is it n -> infty or x -> infty?
n
yep
it depends on what x is, it does exist for some x
Are you required to prove it does not exist formally?
I have to see it in the sense of distributions
Could you elaborate?
Why?
What do you mean advanced?
why?
hes asking this
To prove it wouldn't you need the inverse fourier transform?
alee
and $\int^{\infty}_{-\infty} \delta(x) dx = 1$
alee
and when n -> inf
this happens
oh
So “narrow × tall, constant area” => delta behavior
wait
you can use fourier to say this
wait i think i made a mistake
Where did you get this from?
Let ${f_n}$ be a sequence of tempered distributions. Convergence to a limit $L$ is defined via the duality bracket with a test function $\phi \in \mathcal{S}(\mathbb{R})$:$$\lim_{n \to \infty} f_n = L \iff \lim_{n \to \infty} \langle f_n, \phi \rangle = \langle L, \phi \rangle, \quad \forall \phi \in \mathcal{S}(\mathbb{R})$$
Ajay
[
X(f) = T,\mathrm{sinc}(fT) = \mathcal{F}\left{\Pi!\left(\frac{t}{T}\right)\right}
]
alee
consider this
Let $\text{rect}_n(\xi)$ be the indicator function on the interval $[-\frac{n}{2}, \frac{n}{2}]$. Its inverse Fourier transform is:$$\mathcal{F}^{-1}{ \text{rect}n(\xi) } = \int{-n/2}^{n/2} e^{i 2\pi x \xi} d\xi = \frac{\sin(n\pi x)}{\pi x}$$
Ajay
So, $$\lim_{n \to \infty} \text{rect}_n(\xi) = 1(\xi)$$
Ajay
and since $\mathcal{F}^{-1}$ is a continuous linear automorphism on $\mathcal{S}'(\mathbb{R})$
Ajay
are you proving that $\mathcal{F}\left{1\right} = \delta(f)$ ?
alee
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$$\lim_{n \to \infty} \frac{\sin(n\pi x)}{\pi x} = \mathcal{F}^{-1} { 1 }$$
Ajay
Yes
by definition $\mathcal{F}{\delta} = 1$, which implies $\mathcal{F}^{-1}{1} = \delta$
Ajay
So the limit equals $\delta(x)$
Ajay
i have a question
Ok
since $1$ is not in $L^1$
alee
i dont understand why we can find the FT by doing the limit
since 1 is not in L1
I know that
Yes, the standard integral formula for the Fourier transform fails
yes
That's why I umoved from functions to tempered distributions
i mean why we can do lim T->inf rect(t/T) = 1 and lim T->inf sinc(Tf) = delta(f) and this implies
F{1} = delta(f)
i dont understand why we can do this
that is, is it a Fourier transform in the limit?
Because the FT is a continuous operator on the space of tempered distributions
and why is it "legal" to find a FT this way
can i do another example ?
or i have to open new help ?
You can open a new help channel
i did
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hello ive got this function
so basically
im checking out the symetry
and an e function cant be symetric right
there are many kinds of symmetry, what symmetry are you referring to here?
to the y axis or the other one
i mean like when a normal function has x^ even numbers
then its symetric to the y axis yk
but how does this apply to here
@copper roost Has your question been resolved?
<@&286206848099549185>
the y axis is not an axis of symmetry for f_a, for any a ≠ 0
in order for the y axis to be a line of symmetry the function must be even, ie. satisfy f(x) = f(-x)
but it is easily seen that f(x) and f(y) have opposite signs whenever x and y have opposite signs
ohh yhh
but generally an e function isnt symetrica right?
yeah
a^x is not an even function except when a = 0 and a = 1
btw how do i solve for x = 0
hate this shit
whenever a parameter is involved i dont know what to do
Wdym
the zeropoints
Zeros of the function?
yeah
so we know e ^-ax cant have any right
so we do like 2 parts
and then a^2 * x
idk how tod o that
X =0
A squared is multiplied by X
If you divide by a square it is gonna be 0 I think don't get what your question is
a^2 is a constant so it is just gonna be x=0
omg 🤦♂️
right
ty
i forgot that its connected to x
so its x(0/0) right
the ex^a part doesnt have any x = 0 right
Yeah it can't be equal to zero
@copper roost Has your question been resolved?
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is my substitution method insane or did i do this right
right
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Where would i go to send in a potential discovery i made
I think ive found something
probably a university
in #math-discussion maybe, there's not a place specificably I think

is this abt the super super root thing
you should tell me it
i will tell the relevant people
Se where we go from here chat
Enemy combatant
Enemy combatanant chat
I might make a video start email youtube people
what
From mind your decissions or something
have you read their messages over the past day
you can put it on vixra
Wdym by this
wait im lost, was this the guy who sent the videos in the help channel yesterday?
My messedges have been very thought provoking thak you
what topic is your potential discovery in?
I wanted to ask that tii
yo stay
I cant beleive this
god
Good heavens
if i had gif perms, i would send dies of cringe
Lmao
she claims she found a generalized definition of tetration/pentation to fractional powers
YEAH, in the discussions channel
generalised definition?
are you sure it doesnt exist already?
it doesn't
I found it for roots and logs too
Well, if you've got to ask a mathematical problem you're stuck in, then you can ask, otherwise I'd say move to a discussion channel
For the inverse ops past tetration
as in?
chat if this is legit, we will be noted down in history as the opposers..
And ill prolly try making a youtube vid and email to people
Like mid your decissions
well i am.
i wanna know what they did
do it
😔
i wouldnt go there tho
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I can tell you in dms
hi?
wow I just came at the time where the chat died
interesting reason to leave;-;
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!help
To ask for mathematics help on this server, please open your own help channel or help thread. See #❓how-to-get-help for instructions.
whats your question mate
the restrictions
when there is like a square root for example in an equation
Im struggling w the restrictions
should i give u an example?
so when dealing with the set of real numbers, we know that complex numbers arent defined in the set of real numbers
oh they arent?
so we avoid having a negative number inside a suqare root
they are indeed not
that would be the restriction?
for domain or range tho
precisely
thats where i get confused
You just need to memorize a few rules. For example, you can't have a negative under a square root
you give the machine some input, thats your domain, the machine does its magic, and gives an output
thats your range
oh
yea
ok
i think i get it now
ty
!close
.close
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ty
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Hi
must have been the wind
Do I just flip
putting minus exponents is correct but why
Because I have to follow the rules
true, you're making things complicated for yourself
u can also simplify the two minuses
What you've got on the page is correct.
Are you asked to do something with this?
yeah
the numerator and the denominator both being negative can be simplified, so you get a positive fraction
as for the minus exponents, a minus just means u can replace it with the inverse
so x^-1 becomes 1/x since 1/x is the inverse of x
y^-4 can be written as 1/y^4, since 1/y^4 is the inverse of y^4
does that make sense?
(and vice versa
1/x^-1 is x since the inverse of 1/x is x)
so u can use this rule to simplify and remove the minuses in the exponents
what you did isn't "wrong", it's correct.
but usually when u need to simplify you need to exhaust everything and keep going until you can't anymore
idk if you have to get the ^2 inside tho, seems cluttery
basically $x^n = \frac{1}{x^{-n}}$
doctorstrangejr
(for reference)
i forgot this bot existed
Yeah I know what rule, but cant I just flip them to the bottom to make them positive?
yeah u can
only the things with a minus exponent yes
so the 3 for example stays up
The negative, it bothers me, I didn’t simplify them
I might need your help again on the challenging ones haha
it's a good idea to deal with them as early as possible sometimes, so they don't drag on and make stuff more complicated or unreadable
having to keep track of them can make you cause more errors
@vagrant knot Has your question been resolved?
Hi rat, 54 is kinda weird, can u explain the 3rd step to me
There is a negative and I have to subtract
yeah so its simplified already
Yeah I searched it up
you can't remove the negative anymore
But I didn’t really get it
ah okay
so basically you have 3 minuses in the fraction, 2 of them nullify each other leaving you with only one
the fraction is negative, you can't remove the minus anymore
so sign wise, it's simplified
Yeah
Oh i see, so I just do y^1 - y^8, which is y^-7?
ye
$\frac{-y}{-8y^4.-5xy^4}$
the denomintaor simplifies itself very easily to 40xy^8
is that okay so far?
Rat
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yeah
Yep
what u do is normal subtraction
you take the bigger of the exponents, and subtract from it the smaller one
so if u had y^4/y^3
you subtract 4 from 3,
leaving you with y
if it's y^3/y^4, ud get 1/y
Got it, thanks again
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is this right?
i just used the sinx = cosx rule and cosx = -sinx
y=f(g(x))
dy/dx= f'(g(x)) INTO g'(x)
Yes
wait is it supposed to be let u = sintheta or u = theta?
sin theta
cuz i remember there was a question like tan theta cubed and they let u = theta cubed
u=theta would make no difference
Yeah to make it easier u can use x^3=u
Yeah
alr thank you master yoda
i deeply appreciate your mentoring
its an honour to be your student
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multiplicity of the roots
uhh
wait so wdym
the roots of x^2 are 0 and 0 so we say 0 is a root of multiplicity 2
so
i calculated 3rd root of 2a
then i got a multiplicity of 3
?
no multiplicity is simply how many duplicates of a root there are
so
there are none
here
this is a quartic so it should have 4 "roots"
If that's the actual exercise then you didn't copy f_a(x) correctly
i didnt
oh my god
thanks
@copper roost Has your question been resolved?
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I'm stuck on how I got this answer wrong, as it stated the answer is 919.9 . I thought I was doing the steps correctly, and I'm not sure what went wrong when I was trying to solve it The answer that I got was 785.52, and when rounded to the nearest 10th it was 785.5
why is r equal to 3
Because of the semisphere
what is the diameter of the hemisphere
I'm not sure the question included the diameter, as for the whole question is in the photo on the computer
Like the whole #9 is on the computer, that's the whole problem it gave me to solve
the hemisphere goes across the top of the box
so you should know the distance across the top
The question did not give that to me. Can you please help me see what I did wrong?
Because I showed how I did it on paper, and the computer said it was wrong
you got r = 3 somehow which doesn't make sense; the diameter of the hemisphere is 9 yd
Can you show me a visual..?
the red line is 9 yd
So the hemisphere is also 9 yd?
Yeah, so the hemisphere is also 9yd. But how do I get 919.9 yd^3 as my answer
the diameter of the hemisphere is 9 yd
so the radius of the hemisphere is 9/2 yd
or 4.5 yd
So I would plug that into the calculator
Because I'm still confused on how you're explaining this to me 
Sorry, I just need detailed explaining..
What’s the formula for your model
Just the raw formula
No numbers
it’s the formula of the cube + formula of the hemisphere
Everything I was given was basically on the computer and I had to solve it out. I'm just still confused how it's because explained and how to actually plug it in correctly 💔
$x^3 + \frac{2}{3} \pi r^3$
zain
the main issue is we are trying to show how to find r
Ah
Oh.. so it's 9/2 but why is it that? Since I did 1/2•4/3
Because the sphere volume formula was 4/3 πr^3
why did you pick r as 3
Oh, I see what I did wrong 
Thx for making me see my mistake, I was kinda slow to notice 
.close
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i got -3 but calculator says -2
But x -> 1 so x - 1 -> 0 and ln(x) = ln(x - 1 + 1) ~ x - 1
completely forgor about f(x)^g(x)= e^(g(x)(f(x)-1))
all correct
@round cedar Has your question been resolved?
ln(x) = x-1 wasnt enough here
howcome you got -2
-2 is the correct result, your result was incorrect because the ln(x) = x-1 approximation wasnt sufficient here
oh, then why not approximate it by 0?
it also -> 0
so i was correctly incorrect
you'd need to use the 2nd order approximation here i believe
plz explain further?
when can i use lnx~ x-1 , and when i cannot do so?
and what other alternatives i have..
e^xlnx ≠ lnx
well, you can lhop it
oh you mean before using tricks
ideally, you should always write lnx ~ x-1+O(x^2)
you could also notice that the denominator is 2nd degree, because lnx - (x - 1) ~ x - 1 + O(x^2) - (x-1) = O(x^2)
that means that you have to make your numerator expansion 2nd degree as well
You can get away with using 1st degree for the numerator if you do everything with Taylor expansions, interestingly
uh
how would u do the denominator
You have to do 2nd degree for the denominator
lnx = (x-1) - 1/2 (x-1)^2 + O((x-1)^3)
i dont think you can get away with that
Well, technically you are still taking the 2nd degree expansion of e^(xlnx)
But a 1st degree expansion of lnx suffices for that
MathIsAlwaysRight
that -> -3 already
those degrees yall talking about is related to this "O(x^2)" thing?
um
cuz i aint sure they taught us this
that O(x^2) means that there is a missing x^2 term and further in the approximation
so the degree is 2? because of x^2
oh and i shouldve written O((x-1)^2)
yes
If your approximation worked, you'd expect those O terms to become insignificant in the limit (so e.g. if there was + O((x-1)^2)) in the term, it would be fine, since that -> 0). But if it was e.g. O((x-1)^2) / (x-1)^2, then it wouldnt tend to 0 any anymore, so you'd have to make your approximation better
Oh right nvm, I took Taylor of x^x around 0 instead of 1
that O((x-1)^2) thing just lets you work with the 2nd degree approximation, without bothering to compute the coefficient
and you hope that it will vanish later
which in this case it wouldnt
sadly i still cant get -2
um
nvm
found the error lol
@gloomy river @onyx peak
i think thats cool, thx
.close
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@quartz vigil Has your question been resolved?
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I don’t get this at all
Like I m unable to understand
so when switch is closed capacitor acts like a short circuit
Letting current pass through it
infinitely?
I m so confused ugh
but then after a while it acts as an open circuit
so we ignore the capacitor wire
as if it doesn’t exist?
will u help
🙁
Sry, I don't know this stuff. I was asking for more info to make it easier for a different helper who does know it.
Nobody can help without first understanding where you're stuck after all.
oh
yes, initially - capacitor basically acts like a wire, and once fully charged - acts as an open circuit so u can ignore it.
can u explain me how u would solve
the circuit
then
using this info
I m stuck at this part
@true void
Manish bhaiyya
Initially, replace the capacitor by a wire
Okay
so u basically have R1,R3 in parallel and R2,R4 in parallel right
HOW DO WE FOGURE THAT OUT
Hmm
It’s easy after the capacitor is charged
Just disregard the capacitor and you get two parallel branches
Manish bhayya
I think nodal analysis can be used for the case when it is being charged but not sure
idk hindi lol
So once you replace capacitor by wire, you can see R1,R3 ends have same potentials right
Idk if you can take it as such in the first case
why not
Oh yeah when it has just started charging it acts as a straight wire
Yea but he seems to have a problem in finding that they are in parallel
Hey
Exactly
I don’t get that
how to find what’s in parallel
resistors connected across same potential are in parallel, so here u have R1 and R3 connected across P and Q
and so are R2 and R4
across Q and the bottom point
Basically we find the place where current is being split
?
Okay I get part a now
I got voltage across R1 and R3 as 4.94 and R2 and R4 as 7.06
@true void how about b
For b
like i said you can just remove the capacitor
since it is an open circuit
so now, R1,R2 and R3,R4 are in series
In general things are said to be parallel with both of their ends are joined which is true for these two wires when the Capacitor starts charging
R1 is in series with R2
R3 with R4?
yep
Is my answers for a correct
idk i didnt calculate
yes they are 👍🏻
Voltage across R1 is 4 V
Voltage across R2 is 8 V
Voltage across r3/r4 is 6 V
@true void b?
pls
r u sure
right
Thanks bro
@true void another question
Ok post it
i mightve to leave in a few min tho
I think I m messing up the right hand rule
and the internet has 1000 different versions
Yeah
you know the formula is I(l x B) right
l is in the same direction as current flow
So place your right hand along the direction of l and curl it towards B.
Your thumb will point towards the dirn of force
All of your fingers along current direction, then curl your fingers towards B
right hand only
*make sure your thumb is perpendicular to other fingers.
idk the rhtr version i learnt is this
yes it is cross product
like you said there are multiple versions and the one im talking about does not invlove first finger and middle finger pointing towards different directions
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can someone explain what they mean by (4+h) feet at its ends
that's a frustum yeah
basically, the diameter of the top part is 4 feet
diameter of the bottom is (4+h) feet
cuz h is given to be positive
ok. I see. also what does he mean by "if the axis coincides with that of the log"
this means that the axis of the cylinder is the same as the axis of the log
so if the blue are the axis. then something like this?
the vertical blue is the axis
for a cone we usually don't take horizontal stuff as axii
ok so all there saying is that they are on the same axis meaning the cone is crooked or anyting like that
means the point from where u measure the radius of the cylinder is the same as the point from where you measure the radius of the frustum
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I dont understand demorgans law at all how do I do this
You don't need to understand it to apply it (though you should try to understand it anyway)
i know but what i mean is the 1st one is P^Q why isnt it P ^ ~Q
i also need to understand it because I have a no note exam on thursday
You have the answer key?
Nope i used ai
I'm so tired of people saying that I don't even know how to respond
I dont have any other options we didnt go over a single example in class
litterally the only thing i can do
its tragic
You have search engines that can give you hundreds of pages explaining these things
You have Wikipedia
You also have this server, of course
In no circumstance would I use AI to explain or check maths if I were a student
If i had an answer key id use that its right most of the time and I dont have the time to research anything
,, A \to B \equiv \neg A \lor B
Nel
This is not De Morgan's law, it's just an equivalence that you should remember
Okay
Now for (a), you have P -> not Q
What does that give you if you use this equivalence?
Don't type \ on Discord unless you really want to (you can type \\ to show \)
Use words
So that's not P or Q, right?
yes
Alright?
Basically you distribute the negation and switch between "or" and "and"
so it would be P and not Q?
Yes, if you didn't make a mistake in the previous step
,, A \to \neg B \equiv \neg A \lor \neg B
Nel
This is exactly the same equivalence as before
Just the B from the first one became a "not B"
Okay?
Well that's exactly the same form as P -> not Q
So is this another demorgans law?
Nel
In your case, $A = P$, and $B = \neg Q$
Nel
So it becomes $P \to \neg Q \equiv \neg P \lor \neg Q$
Nel
Does that not make sense to you?
No it doesnt make sense sorry
Can you point to what exactly doesn't make sense? I can't really think of a more basic explanation
Is it the variable substitution?
Okay I dont really know what your tryign to describe like from my pov youre telling me the equivalences and I just dont know what im getting out of that liek why is that important, I just watched a video on demoragns law it only takes place when a not is behind parentheses with an and or an or symbol so i understand that now but I dont know how to convert the regular ones
What regular ones
like in the case of this problem where there isnt an and or an or we are translating its a if then
So translating an if then its called an implication?
Can you tell me what the -> symbol means for you? How is it defined?
Have you learned truth tables?
its conditional and only false if the p is true and the q is false
yeah
Alright, so P -> Q is an expression that evaluates to true or false, specifically it's always true unless P is true and Q is false, which is represented by the truth table of ->
yeah
That -> symbol represents an operation (or operator), just like + represents the addition operation
That operation is called a material implication, or a material conditional
You said conditional just now, so I'm guessing that's how you learned it
Ive only heard it as conditional yeah
Implication means the same thing
okay
Nel
yeah
It has two lines but it's the same as -> in this context
"implies" comes from "implication"
So anyway, when you have an implication, you can rewrite it using only the operations "or", "and", and "not"
This way
so it still means the same thing but you can use or and and not to change it?
Both expressions are equivalent, they have the same truth table
Okay
Nel
yeah ik that luckily lol
Alright
So the exercise is to rewrite the statements in such a way that the negation symbol only appears before variables and not before subexpressions in parentheses
Well in general it's going to be a lot easier to get rid of any implication symbol before doing anything else
wait okay i think im understanding
So not (P and Q) is wait so the not is making the statement false correct?
No, whether a statement is true or false in general depends on the truth values of the variables
oh
What the not operator does is invert the truth value
So "not true" is "false" and "not false" is "true"
okay
"not" is one of the only two boolean operators with one argument (the other being the identity)
Pretty much all the other operators have two arguments (one of the left, one on the right)
You can think of them as functions if that's easier for you
okay
Like the function "and" is defined by:
- and(true, true) = true
- otherwise, and(x, y) = false
But we usually write it in between the arguments instead
yeah
Nel
For (a), since you have $\neg(P \to \neg Q)$, substitute $P$ for $A$ and $\neg Q$ for $B$ in this equivalence
Nel
That gives you $\neg(\neg P \lor \neg Q)$
Nel
Then apply De Morgan's: $\neg(A \lor B) \equiv \neg A \land \neg B$
Nel
Again you need to substitute the variables correctly
So you Have to turn the statement from -> to and or or before you even start it?
In this case yes, in general it's just easier to handle expressions that only contain "and", "or", and "not"
I guess im having trouble translating it at this step then
In this case you're forced to if you want to apply De Morgan's afterward, which you need
Which step? Implication or De Morgan's?
Implication its the one turning it from -> to and or or
Right well that's something you need to memorize
Okay i have it written down for now
(or understand why it's true so you can derive it again)
Like you said yourself A -> B is only false if A is true and B is false, right?
yes
So it's always true when A is false, and also always true when B is true
mhm
,, A \to B \equiv \neg(A \land \neg B) \equiv \neg A \lor B
Nel
You can memorize it like this too
The first step is "A -> B is false when A is true and B is false"
The second step is De Morgan's
okay so this is the rule I need to follow?
To simplify an expression that contains an implication, yes, it's almost always a good idea to do that
okay so with mine not(P ->Q) since its different then the rule one how would i start to translate it
You mean not(P -> not Q) ?
Oh yeah that my bad
If I give you f(x, y) = 2x + 3y, can you give me the expression for f(2x, -y) ?
no..
Well, you may want to review highschool algebra / functions
You substitute a variable for another
In the case of not(P -> not Q), at first we are only interested in the inner expression P -> not Q
The "rule" is "A -> B" is equivalent to "not A or B"
"P" matches with "A", and "not Q" matches with "B"
So the rule becomes "P -> Q" is equivalent to "not P or not Q"
okay
It's literally just replacing all instances of "A" with "P" and all instance of "B" with "not Q"
okay
A and B are variables, but they can represent whole expressions
In this case the only expression that's not directly a variable is "not Q" but in the next question, (b), you will have to deal with two bigger expressions
Just think of A and B as boxes if you will, then you put whatever is on the left of the implication in box A and whatever is on the right in box B
Then you write the equivalence, and finally you simplify
Is there a part I ignore first? like do i just take the inside convert that then apply the not?
i understand the conversions but my example is different then the rule you showed me thats where im stuck theres an abnormality that i have no idea how to solve
okay so as a real life example it feels like your teaching me to swing a baseball bat when in my problem i need to swing a hammer its both swinging but the process is completly different
ive never solved something like this i need examples or steps to take in order to know what to do
I mean... I'm not going to give you a full course on this topic
yes i know its just I dont know what to do next to me this is doing something ive never done before
You have at least three more questions to do from what you posted
Just try to work them out, and if you're stuck, open a channel explaining exactly where you're stuck
I have to go, but I'm sure other helpers will step in if you close this channel and open a new one
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can someone help me with this pls i dont think my teacher taught how to solve this mathematically
i went on desmos and stuff to plot it out and like do it but idk how i do now
<@&286206848099549185>
what properties does a perpendicular bisector have?
it forms a right angle i think
and the other?
yes, so how could you represent that graphically?
and what other line could you draw
from -2,4 to 6,0
and what must be true for them to be perpendicular?
that it forms a right angle
im lost now
what's confusing?
only slope i remember is y = mx+b or something
ok, if two lines are perpendicular, what can you say about their slopes?
that their slopes are equal?
yes please i didnt learn this
ok
basically
if two lines are perpendicular...
||then their slopes, a and b, satisfy ab = -1||
so what can you do?
multiply?
i kinda just assumed it was so no
ok, how could you prove it's isosceles?
(hint: ||distance formula||)
wait, you don't know the distance formula?
no
what do you know?
algebra 2 and sin cos tan
and the sin theorem
last time we were in class (friday before this one) we learned about 3d shapes
ok, i feel like you should know the distance formula...
yeah we didnt learn that at all
anyways, the distance formula says:
the distance between $(a,b)$ and $(c,d)$ is $\sqrt{(a-b)^2+(c-d)^2}$
nadat12
that's the euclidean distance
(proof: it's a corollary of the pythagorean theorem)
the only word i understood was the pythagorean theorem
the distance formula is basically the pythagorean theorem
sorry math isnt my strongest suit i hope thisnt a bother
just in cartesian coordinates
so i would swap about abcd for the coordinates?
yep
and then show that two of the lengths are equal
wait but what coordinates go where
it doesn't matter
the distance formula can be used vice versa*
that is, swapping the points doesn't matter
so $\sqrt{(4 - 6)^2+(2+2)^2}$
