#help-49
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@last slate Has your question been resolved?
@last slate Has your question been resolved?
You can definitely construct one that isn't fully confined
oh yeah nice, what "software" did you use?
desmos
I just read the documentation whenever I needed a certain feature
It's a function that returns a point. If you're familiar with complex numbers, it makes more sense
It basically gives n equal spaces points on a circle of radius s
right i follow that, but is this just boiler plate code?
v is just the "point number" like point 0, point 1
yeah it is
mmmmm interesting
On the topic at hand, I think it is necessarily equilateral
I'm not entirely sure but lemme explain my reasoning
the diagram I sent shows a case where it is equilateral when it's not confined to EFD
hmmm wait are we sure that's how you would draw the diagram?
okay wait your case is a special case,no?
It's one case
Idk then tbh
Ohhhhhhhhhh
I didn't think about the triangles not necessarily oriented is a similar way
i still don't get how to draw it tbh
😭
i suck at geometry arghhh
how did they draw that
is this any help?
no i mean probably dumb question but it's late for me
how do you draw that on paper
or whatever
oops, error
what's the motivation to draw it
Well if you really wanted to, you could use a ruler and a protractor to draw the EFD.
The angle DEA, BFE, CDF are the same so there's that
no no
how do i make a sketch of it lol
for this i first drew ABC
then i just drew outward triangles BCF, ACD, and ABE
then connected the vertex of each of those outward triangles and got DEF
i don't care about the exact measurement ofc
i just have to draw a sketch
but i can't think of how to draw a sketch of however the ABC thing will look like after it's out of DEF
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just reflect A in line ED and join up the points
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cat, nut, not, act, art, bat
this is an unique arithmetic sequence, where a letter corresponds to a number.
determine the next word in this sequence
hm
so c, n, a, and b are consecutive
The tens digits also jump from c to r to a
so r=n
cat nut not act ant bat
you also go from a back to a in five numbers
So the common difference is a multiple of 20
probably either 40 or 60
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f is a function of R^3, how can i show this?
do you now the domain and codomain?
hum i guess yes
it is just write that it's a function of R^3 so i guess the domain and codomain are R^3
it doesn't look like f is just any function
perhaps you mean to specify that it is linear?
it's not write but we can assume it, what do we gain with the linearity
well nobody talks about kernel and image for non-linear stuff
ye that's true
For the problem, start by showing that ker(f) and im(f) do indeed make a direct sum (show that their intersection is {0}).
Then you can use a really nice theorem about the dimensions of kernels and images :p
that's the part i'm strugling with
x€Ker so f(x) = 0
and f^3(x) + f(x) = 0
idk what to do with that
Take some element y in both ker(f) and in im(f). You want to show that this has to be 0.
If it's in ker(f), then f(y) = 0.
If it's in im(f), then there is some x such that f(x) = y.
You'll want to use both of those, along with f^3(x) + f(x) = 0 to get to y = 0.
ok i made it
for the second part we're using the fact that we are in finished dimension
Yeah. The direct sum is a subspace of R^3, and you can get its dimension from what you constructed.
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hello
@sharp wave Has your question been resolved?
<@&286206848099549185>
i substituted the values of f(x) and f(pi/2-x) but then im stuck on how to simplify
prolly we need tfc1,no? but i cant manage to put all the pieces together
tfc1?
should i write it down?
and show you guys
we have been taught a property but that dosent help
over here
okay let me try
how does that work
youre stuck with a sin2x term right
wait should we sub 2x as u maybe thatll work
since the lim its then come in the asnwers format
no
do partial fraction decomposition first
that way you can separate out the x and pi/2 - x
but there are still two terms in the numerator no
wait let me try i like this
yep that worked @neat hamlet
i still had to sub 2x as u though
thank you so much both of you
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prove that $a^n|b^n \implies a|b$
ƒ(Why am. I here)=I don't Know
without prime factorisation
I would like to use EDA if possible
eulclds division algorithm that is
so I have $b^n=da^n$
ƒ(Why am. I here)=I don't Know
I was thinking of equating b^n/a^n to some integer k^n
then take the nth root of both sides
yeah, I know
I feel like you’ve been told this many times but for some reason you insist on using fractions
sorry
hm, im not sure how Euclidean division could help..
alternatively bezout's lemma may help
my book does have a hint,just as minute
put d=gcd(a,b) and write a=rd, b=sd where gcd(r,s)=1. my part (a) gcd(r^n,s^n)=1 . show that r=1 whence a=d
part (a) is if gcd(a,b)=1 then gcd(a^n,b^n)=1
oh huh, interesting
problem a is if gcd(a,b)=1 then gcd(a^n, b^n)=1
cant u show the contra positive easily
that is if a|b \implies a^n|b^n
hmm how would you show the contrapositive?
Do you know how to do this?
yeah, bezout's lemma
let me try
ok wait this is hard too :(
I'm not too sure, but I guess bézout's lemma
so try to use a^n | b^n
ƒ(Why am. I here)=I don't Know
assume a doesnt divide b
so there exists some p^w that divides a that doesnt divide b. the p power in b is <w. looking at the p power of a^n is >=wn. while p power of b^n is <wn. thus a^n doesnt divide b^n
that works?
what?
I don;t follow
I feel like I should try to understand EDA once more I thought solving problems would help, but doesn't seem like it's helping
can I close this for now?
sure
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https://math.stackexchange.com/a/696537/879009 could someone explain this?
ƒ(Why am. I here)=I don't Know
hmm, if gcd(a,b)=1
no, I get that, but how is $ab=-a^2$
ƒ(Why am. I here)=I don't Know
it isnt
its just with gcd there are some properties that allow u to get from one part to the next
ah
ok
How am I supposed to know this identity if I've never seen it before, is it supposed to be obvious?
Another way to see it
Is the euclid algorithm
To compute gcd(x,y) you compute the remainder of y/x
And so on until you reach 0
yes
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I'm having a hard time understanding this
so the only elements of the field are -\infty, 0 and \infy?
no
it's all real numbers, as well as ∞ and -∞
ah
and it's not a field
so it's. a vector space?
what makes you think that?
oh right
check the vsp axioms 
that's the question
ah
OK, I think I have a rough idea of how to do this now, let me TeX a proof
so we'll have to prove teh following 1) Commutativity, associativity, additive identity, aaditive inverse, multiplicative idenrity and the distibutive property
lots of things to prove
- commutativity
\
$a+b=b+a$ , from the defn it follows that $\infty+a=a+ \infty$ and the same for negative $\infty$
2)associativity : $(a+b)+c=a+(b+c)$ over R and as any number + $\infty$ is \infty the same holds true as one or more variables tends to infty - 0 is an element by defn
- as is1
ƒ(Why am. I here)=I don't Know
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TeX massacred
oof
- commutativity
$a+b=b+a$ , from the defn it follows that $\infty+a=a+ \infty$ and the same for negative $\infty$
\
2)associativity : $(a+b)+c=a+(b+c)$ over R and as any number + $\infty$
\is $\infty$ the same holds true as one or more variables tends to infty
\ - 0 is an element by defn
- as is 1
ƒ(Why am. I here)=I don't Know
for example for commutativity, you have the case where a and b are both real numbers, and the case where a is ∞ or -∞
there's still another case
$\pm \infty \pm \infty = \pm \infty$
ƒ(Why am. I here)=I don't Know
and $\infty - \infty =0$
ƒ(Why am. I here)=I don't Know
right
so if a and b are equal
then commutativity is obvious: a + b is clearly equal to b + a
so the only case you need to consider is ∞ + (-∞) = (-∞) + ∞
which is fine bc they're both 0
so commutativity is good
what about associativity
That's true over R and true at $\pm \infty$ as $ a+ \pm \infty = \pm \infty$
ƒ(Why am. I here)=I don't Know
I don't know what you mean by that
there are three different variables in the statement of associativity
(a + b) + c = a + (b + c)
which ones are in R and which ones are infinite, in what you are considering?
(a+b)+c=a+(b+c) is a property of R
okay, so that handles the case where a, b, and c are all part of R
what about the other cases?
actually more
I guess I can prove it for one case and say it's simialrly true for all other cases?
(you should also be able to tell when yo'ure done, ofc)
why?
why would the other cases be similar
one var is \pm \infty the other two belong to R
in the next case two vars are some form of infty and the other blongs to R
write it out
yeah, let's consider that first case where one var is ±∞ first
$\infty+(a+b) = \infty = (\infty+a)+b= \infty )$
ƒ(Why am. I here)=I don't Know
I think you wrote it a little weirdly, but good
uve an extra ) but its goos
I would've written something like: [\infty + (b + c) = \infty = \infty + c = (\infty + b) + c]
biased_estimatERIC
and then the same proof works for a = -∞
what about if b is ±∞, and a and c are real? does it also work
yes
yeah, it works simialry for all cases
write it
yeah, it's good to practice writing it out
even if it may seem tedious
associativity is often hard to check because there are three variables involved!
yeah, Wrote it in my notebook
okay can you show me
uh, it's kind of messy, let me re-write it
alright
okay yeah that looks good
btw isn't this not exactly exhaustive
u need more details no?
there's still more cases, yeah, if that's what you mean
yea
yeah, I realise there are 3 possibilities for each variable, so 27 possible cases
I'm assuming b, c are real for that case
yeah, a lot of them are similar, but not all of them are similar
what about the options where both a and b are infinite now? (and c is a real number)
this is where it might get tricky 
that's still \infty
i mean inf in the middle or last position
I'm assuming a = ±∞ for that case; I made him do the other two positions in the picture he sent (b = ±∞ and c = ±∞)
ah i see thats good
now to prove the distributive property for the additive identity and multiplicative identity are trivially ture, right?
hang on
stay with associativity
did you consider the options where a and b are infinite, and c is a real number yet?
I did , I got $\infty$
ƒ(Why am. I here)=I don't Know
$(\infty + \infty)+c = \infty +c =\infty=\infty+(\infty+c)=\infty$
\
$(- \infty + \infty )+c=0+c=c but - \infty+(\infty +c)= -\infty+\infty =0$
\
how does that demonstrate the associative property?
oh, right
associativity is
(a+b)+c=a+(b+c)
ƒ(Why am. I here)=I don't Know
so then what can you conclude
this isn't a vector space
good! because associativity doesn't work
intuitively, you can think of adding infinity as "losing information"
if you start with some real number c, then add infinity, then subtract infinity, you lose track of the original number c was
that's not possible in a vector space
I see. yeah, makes sense
any addition operation is perfectly reversible in a vector space
thanks!
(more generally, in what's called an "abelian group" this is also true)
(but don't worry about that too much right now)
I pressume group theory is a late undergrad course?
it's an undergrad course
when you take it in undergrad depends on your interests and school
you're welcome! you're doing well
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good job
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find a condition a,b and c so that one zero of ax^2+bx+c is the square of other
Let me tell u my side first
basically
it is saying one should be alpha so other should be alpha^2
right?
sum = alpha + alpha^2 = -b/a
product = alpha X alpha^2 = alpha^3 = c/a
but what after that
kheerii
What variable do you wish to eliminate from this?
$\alpha^3=\alpha^2 \alpha$
Samuel
^^^
$\alpha+\alpha^2=-\frac{b}{a}, \alpha^3=\frac{c}{a}$
Thor
@urban prism Has your question been resolved?
<@&286206848099549185> 15 mins have passed so
guys what is a good game rn which is like either a city game or maybe like a vintage old game or vintage old military related stuff in roblox
??
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I need help
Distribute it first
okay so kx^2-56x = -16
so would it be kx^2-56x+16=0?
Yes it would
but what is the least possibel
Now do you know delta ?
no im in 9th grade
The discriminant ?
b^2 - 4ac
You apply it to the quadratic you got
Yes so let k as it is
The a value is k
wait is < 0 one solution?
No its no solution
The one solution is when the discriminant = 0
but why do i have to solve for no solution
Cuz they ask for
srry im confused on this part
ohhhh
wait yeah wait icic
but after you set it as less than what do you do
You have 56^2 -4k*16 < 0
mhm
You solve for k
I think you forgot to turn the inequality sign no ?
When divided by a negative numbers
There you go
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can someone explain why
yeah
so... when t = 0 (initially), you have P(0) = (C)(2)^0. Agree?
yes
so C = 12000, agree?
wait what?
Ok so P(4) = 24000 = 12000(2^(4r)), agree?
this
yes
you can take log. or you can just realize that 2^(4r) = 2^1, and conclude that 4r = 1
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Can someone tell me the answer for this
Have you tried solving it?
more precisely when x < -2, but yes
But if I multiply -1 here
or (-7 - root(17))/2
ya
K
then x = (-7-root(17))/2
Ohh
is the only solution
Thx bro
Do you know why x < -2?
Absolute value
yep
But how is it
For the first mod 3 is absolute value
And for the second -1
How is it -2
what do you mean by "mod"? Case?
Modulus
for the 1st one we have |x+2| then x = -2
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let $a<b$, where a and b are positive , show $a^2<b^2$
ƒ(Why am. I here)=I don't Know
I mean this is obviosuly true
let b=a plus some constant k
Same question
Not too sure tbh
am working on it now
just like working on discord
oh
do you have any axioms to work with?
I guess you’re allowed to multiply by a positive number by both sides of the inequality?
k > 0
m < n => km < kn
This should be enough to prove it
yeah, this
I was actually thinking of arguing if b>a adding b to it self b times will be more than adding a to itself a times
that works only for integers
oh,right
eh its nt anyway
adding b to it self b times
adding a to itself a times
apparently not
lang's calculus is it?
A first course in calculus
calculus yes
couldn’t you use geometry since both a and b are positive and can be used as side lengths?
Try and see if you can find this @twilit field in the textbook
you could
i could
i dont have a copy of the textbook so idk what lang covers
I'll check
there a few rules
if a>b and b>c then a>c
if a>b and c>0
then ac>bc
I suppsoed I could use this
those are sufficient actually
dont flip your signs
Yup
do you mean a^2 < ab?
this, otherwise it's correct
is it normal to miss the obvious stuff while just starting college , haven't have had to think in such an elemenatry way in a while
thanks everyon!
You got it quite quickly after looking at the axioms
Yeah I think you’re always doing very well the times I chime into these help channels
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if a/b<c/d , show that a/b<(a+c)/(b+d)
I just cross multiplied and got back the oG inequality
is there any other way to do this?
You can reverse those steps
Can you assume all a,b,c,d>0?
oh yeah, that too
so I start with ad<bc
then I add ab to both sides
and I'm done I think
thanks
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so to start let $v_1,v_2\in V_c$
where $v_1=a+bi$
$v_2=c+di$
then $v_1+v_2 =(a+c)+(b+d)i$
similarly $v_2+v_1 = (c+a)+(d+b)i$
these two req equivalent due to the commutativity on $\R$
ƒ(Why am. I here)=I don't Know
Yeah
just a minute
now to prove associativity
let $v_1 and v_2$ be defined the same way they were above and then we have $v_3 =e+if$
so$ (v_1+v_2)+v_3_= ((a+c)+e+i((b+d)+f)$
and $v_1+(v_2+v_3)=(a+(c+e))+i(b+(d+f))$
which are once again equal due to the laws of associativity on $\R$
ƒ(Why am. I here)=I don't Know
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Yea
next let $v_1= a+ib ; v_2=0+0i$ so we have $v_1+v_2=a+ib$, but this doesn't prove the existance of an additive identity
ƒ(Why am. I here)=I don't Know

yes it does you just wrote it down
you just showed that there is some vector such that you add it to any other vector you get that vector back
also i should note that everything you are doing is essentially identical to how you (presumably) showed C is a vector space
yeah, that's essentially the question
for the existance of an additive inverse let $v_1 =a +ib ; v_2 =-a+-ib$ so $v_1+v_2=0$
ƒ(Why am. I here)=I don't Know
now to prove the existence of a multiplicative identity if $v_1=a+bi$ and $v_2=1+0i$ then $v_1 v_2=v_1 proving the existance of the same$
ƒ(Why am. I here)=I don't Know
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thanks everyone!
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How do I ask for help
ahuh
I thionk I got it
Cuz
im currently doing my onine math test
did I get this right?
and dis
it's against server rules to ask for help for a graded assessment
@chrome root Has your question been resolved?
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$\lim_{x\rightarrow a}\left(f\left(x\right)+g\left(x\right)\right)=\ \lim_{x\rightarrow a}f\left(x\right)+\lim_{x\ \rightarrow a}g\left(x\right)$
ƒ(Why am. I here)=I don't Know
Look at the proof for sequences
without epsilon-delta limits
👍
Hey wai
what exactly should I look up??
hey
The proof that you can split the limit of a sum of two sequences if both limits exist
This is only true if both limits exist, which is important
I know that
Yeah that’s what I was thinking too
so for now I just accept it as a fact?
I mean it's obvious
I could probably learn epsilon delta limits

thanks
Honestly it’s like 2 lines lmao
I know, but I've never done epsilon delta limits before
thanks again everyone
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Hmm, the sequence one is also using epsilon delta?
yeah
Can you show me
there's no delta to talk of
Oh, hmm
I guess it’s just the same as a normal limit
What
when i proved that stuff there was no delta
I think epsilon-delta is only for limits of functions
Huh?
ok, I don't know how to solve epsilon limits either
yeah
Or there isn’t an epsilon rather
what
If you’re taking a limit to infinity you don’t use |x-a|<epsilon, you use x>N
I have no idea what that means
When you study epsilon delta proofs you’ll understand
Thanks a lot though
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Please solve it
I might be offline so please solve fully. I tried solving it but could only work out 2 ordered pairs, one is (1,2) and second is (2,1).
Well, I did get solutions so-
And it's only against the rules if you haven't fully solved the question, but if you have then you might. Still, I'll try to work with a hint if that's the best I can get.
!show
Show your work, and if possible, explain where you are stuck.
The show ur work instead
This is my work ;-;
I got (1,2) and (2,1)
So u didn't solve it
But then it will be (phi,1) or (phi,2) and A union B won't be {1,2}
It's gonna be either {1} or {2}
I guess
I'm confused
why's B gotta be {1} or {2}
A and B are sets
np
I got 9 elements
Combinations of A and B*
Oh
Wait
4 combos
Because others have phi as an element which will not satisfy the condition
Lemme fheck the answer
Oh ;-;
It's 9 for some reason
Read the question again
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Have I proved it the wrong way around
is def'n 2.2.3 just that of a sequence converging to its limit?
yeah
then yeah, you did it the other way around. you used that which you wanted to prove as an assumption
also you never declared a positive epsilon
so we don't know who this epsilon character is on mathy line 2
Does this fix all of that?
we ignore the first line you write because it assumes the conclusion. also, the algebraic step between 2 and 3 may be unclear
Oh yeah the first line
multiplying 2/3?
I guess it depends lol
Yeah I've done worse before
I think I'll let it slide
that's fair
there's a better procedure that doesn't incur the handwaviness at the end
you just massage the inequality of (2) a bit to look like (2x_n - 1)/3 converges to 1
I guess I could do some triangle inequality stuff
that's not necessary either
Huh
2x/3 - 4/3 = (2x-4)/3 = (2x-1)/3 - 1
and abs((2x-1)/3 - 1) < epsilon for all n >= N, hence (2x-1)/3 converges to 1
rad
I was typing up a comment about using a colon after the N on the first line but I rescind it lol
I think the colon is good and fixes a problem that I have
wherein me using a comma in place of a colon on the first line (such that for all n >= N{: -> ,}) makes me want to treat the math mode stuff like a sentence and thus put a period on the last math line in (3)
probably not but I figured I'd share my thought anyway in case you had any more insight about the usage of the colon lol
pog, np
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Help for d and e pls
its tech active so i can use my cas to find the discriminant, but i need some guidance
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how do I solve the last question?
I tried doing it by subbing 0.004 as s and find for t but it gives me a decimal like 0.0666687... and that is clearly not correct
how are you suppose to do this?
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prove that $x-\frac{x^3}{6} \leq sin(x)$
ƒ(Why am. I here)=I don't Know
my first idea was to say that x-x^3/6 is only a part of sin(x)'s taylor expansion
or alternatively, first find the derivative of both sides
to obtain $1-cos(x) - \frac{x^2}{2}$
ƒ(Why am. I here)=I don't Know
are you allowed to use taylor series?
I know taylor series, but haven't covered it yet in the book so idts
this is the same as $2sin^2(x/2) -x^2/2$
ƒ(Why am. I here)=I don't Know
This is only for $x \geq 0$?
Pseudonium
yes
ƒ(Why am. I here)=I don't Know
Also this is false for $t \geq 0$
Pseudonium
i think
,w is x>sin(x)
just using a counter example would be fine
It’s true for x > 0
But i assume you need it to work for x >= 0
as t=x/2
that's why it's $\leq$ here
ƒ(Why am. I here)=I don't Know
Yeah so why not just do $\sin x \leq x$
Pseudonium
from here, to move foward , I need to sub x/2=t
right
to bring it to this form
Oh yeah sure
But I don’t see how you get from that back to your original thing
Like I totally agree that $2 \sin^2(x / 2) - x^2 / 2 \leq 0$
Pseudonium
And I agree with your proof strategy of setting $t = \frac x2$ to do this
Pseudonium
$2sin^2(t)-2t^2<0$
ƒ(Why am. I here)=I don't Know
or $sin^2(t) \leq t^2$
ƒ(Why am. I here)=I don't Know
But how do we define sin(x) if not with Taylor series
You seem to keep introducing strict inequalities when they’re unnecessary
lang has defined it as $\frac{y}{\sqrt{x^2+y^2}}$
Right, so you do need the second one
or using a triangle
And you know why both are true?
Missing } at the end
yes
Ok cool
ƒ(Why am. I here)=I don't Know
in a right triangle
Lol
And what’s y
side length of opposite side
But surely then x is not the input
You’d need it to be the angle
You need to define a function $\text{sin} : \mathbb{R} \to \mathbb{R}$
Pseudonium
x isn't the input here
it's the adjacent side
geometry
I feel like I’d want to approach questions with sine using the definition of sine given
Like how do you know this is true
You’d want to refer to the definition of sine
hmm?
As in
then that raises the question
Yeah in an earlier question they said it was given
how did you prove that result 
Given a real number t, you need to be able to give me the output sin(t)
derivatives
Otherwise im not convinced you have a function
Hey I was gonna sweep it under the rug and not look
But now you’ve opened the can of worms
Because, after all, a function is supposed to send inputs to outputs
sin(x) can't really be defined wrt to its input without taylor series afaik
Well I mean idk dude you want to use sine in a question you better give me a definition
this
Otherwise we’re gonna just pull random facts out of our ass
This definition doesn’t meet my requirement
How do I use this definition to find sin(1)?
Im pretty sure sinx < x is a given fact, they stated that in an eariler question
“Given fact”
Yeah that’s fine
no, I proved it, I can prove it again if needed
damn
you can't, I'd probably use the unit circle in that case
If you can’t tell me what sin(1) is, you haven’t prescribed to me a function
In order to define a function you must tell me where every input goes
If I have a particular input I must be able to compute the corresponding output
I'm not sure how I'd do that without the taylor series
except when you dont due to uniqueness theorems 
But Taylor series are the most convenient
yeah, but they are geometric , right?
But don’t uniqueness theorems tell us where things go in a round about way
And define $\sin(x)$ to be the solution satisfying $y(0) = 0, y’(0) = 1$
Pseudonium
are you a constructivist 
This is a perfectly legitimate definition of sin
true
Pseudonium
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cant we just assume the inequalities and move on 
anyway, should I prove sin(x)<x first?
If you say you’ve proved it it’s probably fine
ok, so in that case is my proof fine?
Pseudonium
However I don’t see how you get back from this to your original statement
$2sin^2(t)-2t^2\leq 0$
ƒ(Why am. I here)=I don't Know
so $sin(t) \leq t$
ƒ(Why am. I here)=I don't Know
or $-sin(t) \leq t$
ƒ(Why am. I here)=I don't Know
Yeah no I totally agree you’ve proved this (I think)
Although the way you phrase it is a little annoying…
Really, you should convince me that, starting from $\sin(t) \leq t$ and $- \sin(t) \leq t$, we can deduce $2 \sin^2(t) - 2 t^2 \leq 0$
Atm you seem to be proving things backwards
Which, I’m not sure if you’re good enough at proofs for me to trust that you know what you’re doing
$\sin(t) \leq t$ and $- \sin(t) \leq t$, we can deduce $2 \sin^2(t) - 2 t^2 \leq 0$
Ok, why?
the TeX it bot is down?
Yeah I was wondering
so from $sin(t)\leq t$
