#help-17

1 messages · Page 269 of 1

minor rivet
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oh

dense cedar
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cos would work

minor rivet
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wait so how do i start the question aft drawing

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idk what to find 1srt

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Omg nvm i see

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wheres the right angle tho

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im lowk tweasking out over this question

dense cedar
dry lynx
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in your diagram AD and AC should be tangents

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yeah

dense cedar
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The channel was just lost, huh !

minor rivet
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but how do u know if its a eright angle tho

dense cedar
minor rivet
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idk the tangent rule thing 😭

dense cedar
dense cedar
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Okk?

minor rivet
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OHHH I SEE

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that makes sm sense tysm 🙏

dense cedar
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Wlcmm

minor rivet
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TYTYT I HAVE BEEN STUCK ON THIS FOR 3 HOURS

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ok i will close

#

.close

vocal sleetBOT
#
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onyx marsh
#

$(E-F)\cup (F-E)\iff (x\in E\land x\notin F)\lor (x\in F\land x\notin E)\iff [(x\in E\land x\notin F)\lor (x\in F)]\land [(x\in E\land x\notin F)\lor (x\notin E)]\iff [(x\in E\lor x\in F)\land (x\in F\lor x\notin F)]\land [(x\in E\lor x\notin E)\land (x\notin F\lor x\notin E)]\iff (x\in E\lor x\in F)\land (x\notin F\lor x\notin E)\iff (x\in E\cup F)\land (x\notin E\cap F)\iff x\in (E\cup F)-(E\cap F)$

twin meteorBOT
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pirateking0723

onyx marsh
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is this correct

tidal dock
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oh god

onyx marsh
tidal dock
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$(E-F)\cup (F-E)\
\iff (x\in E\land x\notin F)\lor (x\in F\land x\notin E)\
\iff [(x\in E\land x\notin F)\lor (x\in F)]\land [(x\in E\land x\notin F)\lor (x\notin E)]\
\iff [(x\in E\lor x\in F)\land (x\in F\lor x\notin F)]\land [(x\in E\lor x\notin E)\land (x\notin F\lor x\notin E)]\
\iff (x\in E\lor x\in F)\land (x\notin F\lor x\notin E)\
\iff (x\in E\cup F)\land (x\notin E\cap F)\
\iff x\in (E\cup F)-(E\cap F)$

twin meteorBOT
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artemetra

tidal dock
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looks correct.. the only way i see how to simplify this further is by writing it as symmetric difference

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$E \triangle F$

twin meteorBOT
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artemetra

tidal dock
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finally lol

tidal dock
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but otherwise looks to be all good

tidal dock
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this symbol

onyx marsh
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to let it take fewer steps to reach the other side ?

onyx marsh
tidal dock
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yeah it's what your final expression is equivalent to

onyx marsh
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in fact i am trying to prove that $E\Delta F=(E\cup F)-(E\cap F)$

tidal dock
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huh

twin meteorBOT
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pirateking0723

tidal dock
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oh

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yeah then you are good

onyx marsh
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given that $E\Delta F=(E-F)\cup (F-E)$

twin meteorBOT
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pirateking0723

tidal dock
onyx marsh
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.close

vocal sleetBOT
#
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vocal sleetBOT
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upper harness
#

The question is about the calculation of a basis of the kernel of a linear function - ker(l)

I dont understand what's the link between the the solution of the system and the two vectors that make up the basis

hard atlas
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after solving for all the entries a vector in the kernel can be written as (-x5,0,0,x4,x5)

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yes?

upper harness
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i dont see why x4 and x5 are inclued in the end though

hard atlas
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x5 can be chosen arbitrarily

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as long as x1 is chosen as -x5

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similarly x4 can also be chosen arbitrarily

upper harness
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that's because they were moved on the RHS at the start

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right?

hard atlas
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well they were moved right because of it

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so kind of the other way around

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(and moving them to the right is a bit of an odd step imo, you dont need to do that)

upper harness
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i copied this from a solution sheet made by my prof

upper harness
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so how do I get those two column vectors as the basis

hard atlas
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good

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this can also be written as x4(0,0,0,1,0)+x5(-1,0,0,0,1)

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yes?

upper harness
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i dont see it

hard atlas
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(0,0,0,x4,0)+(-x5,0,0,0,x5)

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this?

upper harness
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ok

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but I still dont get why they're being separated

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and the first -x5 doesnt appear in the first vector

hard atlas
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I chose to split them up that way instead of another way

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another way would also be valid but not as useful

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now I have two vectors, one with only x4 and the other with only x5

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which means I can move those factors out

hard atlas
upper harness
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aha ok

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you chose to split them like that to make it tidier

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variable segregation

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let's say

hard atlas
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but if we now look at this from a different perspective, this means that any vector in the kernel can be written as (some number)*(0,0,0,1,0)+(some other number)*(-1,0,0,0,1)

upper harness
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(english isnt my first lang**)

hard atlas
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aka as a linear combination of (0,0,0,1,0) and (-1,0,0,0,1)

upper harness
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ok i'm starting to see it

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I'm going to try a new one and I'll come back in a bit

hard atlas
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and those vectors are obviously linearly independent

upper harness
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can I ping you just in case?

hard atlas
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so therefore they are a basis of the kernel

hard atlas
upper harness
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ok

#

tysm

vocal sleetBOT
#

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upper harness
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Can somebody tell me if this is correct?

vocal sleetBOT
upper harness
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@hard atlas

hard atlas
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yes thats a correct basis

upper harness
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thank you for the feedback

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can I dm you?

hard atlas
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stay on the server

upper harness
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ok

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I'll try a couple more and I'll ask for feedback

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@upper harness Has your question been resolved?

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bitter pilot
#

Help

vocal sleetBOT
twin meteorBOT
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𝔸dωn𝓲²s

hard atlas
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list all the elements

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Z_12 is cyclic so the other one would also have to be

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what could a generator be?

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what do you know about homomorphisms and generators?

bitter pilot
hard atlas
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you sure?

bitter pilot
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either (2,1) or (1,2)

signal pendant
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well look at what happens to the second slot as you keep on adding (1,2) with itself and then argue why it cant be a gen

bitter pilot
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ok it doesnt generate 2,2

bitter pilot
hard atlas
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there is a much easier generator

hidden gyro
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both of them are the same

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just inverses

hard atlas
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if (a,b) generates Z3 x Z4, then a needs to generate Z3 and b needs to generate Z4

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at the very least

bitter pilot
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is it that simple?

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or just necessary

hard atlas
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just necessary

hidden gyro
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nevvessarry

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actually with 3 and 4 it is also sufficient

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ig

signal pendant
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are you aware of the chinese remained theorem? by any chance?

bitter pilot
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heard of it

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but not really know

signal pendant
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okay dont mind that but as denascite said there is a very obvious generator which for some reason you didnt try, and it will justify why your map is an isomorphism

bitter pilot
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1,3?

signal pendant
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is that really the first thing you thought of

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whats the most naive guess you can make

bitter pilot
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as if it was really 1,1

hard atlas
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it is

bitter pilot
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no way

signal pendant
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why dont you check

bitter pilot
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i did

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my head doesnt work lol

cobalt crypt
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,w Table[{n mod 3, n mod 4}, {n, 0, 11}]

bitter pilot
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my first intial thought was 1 from Z_12 is a generator and would map to (1,1)

bitter pilot
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but (1,1) I thought I would only get pairs like (1,1) (2,2) and (0,0) for some reason

signal pendant
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in fact if you trusted your map this should be the first generator you find

lilac pebble
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f(a,b)->a+b isn't onto

cobalt crypt
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f(a, b) = a + b isn't well-defined

bitter pilot
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what does well defined mean

cobalt crypt
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it means that the definition actually makes sense

signal pendant
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it is better if you define your map in the reverse direction but you can make this work too

lilac pebble
hard atlas
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there are several ways to write the element (a,b) in Z3 x Z4

cobalt crypt
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by not defining it that way

hard atlas
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not all of them would give the same value for f

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for example, (1,3)=(4,3) but they have different sums

cobalt crypt
bitter pilot
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SO

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Z_12 -> Z_3 x Z_4

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that was also my first thought 😭

cobalt crypt
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f(a, b) = the solution x to x = a mod 3, x = b mod 4

hard atlas
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whenever you have some object which came from some equivalence relation you have to make sure that the way you write an element does not influence the value of the function

signal pendant
cobalt crypt
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Z_12 -> Z_3 has an "obvious" map which is the mod 3 map
Z_12 -> Z_4 has an "obvious" map which is the mod 4 map

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that should be your first choice really

bitter pilot
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two maps??

cobalt crypt
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to map into a product, you need two maps

signal pendant
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making them into one is why you producted them(the groups)

cobalt crypt
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one to each component

bitter pilot
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oh

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makes sense

twin meteorBOT
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𝔸dωn𝓲²s

hard atlas
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(note that this is well defined, if you take a or a+12 or any other way to write the same element of Z_12 then f(a) still has the same value)

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which is important because if you want to check that its a homomorphism then you have f(a+b) where a+b could be "bigger" than 12 and if you then had to make sure that you took the "correct" representative it would be a huge pain

bitter pilot
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wow

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The proof is a lot easier now, I think

vocal sleetBOT
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@bitter pilot Has your question been resolved?

bitter pilot
signal pendant
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your proof of surjectivity is not a proof but the good part is you dont need it. also why does 3n = 4m imply n=m=0

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i can have n = 4 and m = 3 for example

bitter pilot
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I am so bad at this

cobalt crypt
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did nobody tell you that a homomorphism is injective iff its kernel is 0

bitter pilot
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true

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f(x) = 0

cobalt crypt
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when you do algebra, nobody ever checks f(x) = f(y)

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its always f(x) = 0, prove x = 0

signal pendant
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and here it is especially easy to check this condition. (just check every element)

cobalt crypt
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i mean

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if x = 0 mod 3 and 4, then x = 0 mod 12 because 3 and 4 are coprime

signal pendant
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yeah

bitter pilot
signal pendant
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you dont need to prove surjective

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think about the cardinalities of each set

cobalt crypt
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for finite sets, injective, surjective, bijective are all equivalent

bitter pilot
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right..

cobalt crypt
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in fact, that is how you can characterise finiteness of a set

lilac pebble
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you're assuming the sets are of the same size, right?

cobalt crypt
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endos

signal pendant
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no

lilac pebble
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endos?

cobalt crypt
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,w endomorphism

cobalt crypt
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i guess here its not an endo

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but the sets are still the same size

signal pendant
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Z_3xZ_4 and Z_12 have the same cardinality

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we are not assuming anything

bitter pilot
lilac pebble
signal pendant
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or do you mean the thing about injective bijective surjective being equiv

cobalt crypt
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that statement was for endomorphisms

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in my mind i had already identified the two sets kekehands

bitter pilot
signal pendant
cobalt crypt
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T

bitter pilot
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I have to see whether [ (\mathbb{Z}_{12}^, \cdot) \cong (\mathbb{Z}_3^ \times \mathbb{Z}_4^*, \cdot). ]
I have the feeling it is, I will get soon to it!

twin meteorBOT
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𝔸dωn𝓲²s

vocal sleetBOT
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@bitter pilot Has your question been resolved?

twin meteorBOT
#

𝔸dωn𝓲²s

bitter pilot
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Is this enough of a proof?

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besides the fact that they have the same cardinality

twin meteorBOT
#

𝔸dωn𝓲²s

bitter pilot
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yea it worked out but i still wonder if the above is sufficient

cobalt crypt
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you have to check that it's a homomorphism

cobalt crypt
bitter pilot
cobalt crypt
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yeah so then you have to check it's a homomorphism

bitter pilot
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ok!

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I think it is using the definition of direct product

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gimme a sec

twin meteorBOT
#

𝔸dωn𝓲²s

cobalt crypt
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yeah

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those in the know would just say that Z_12 and Z_3 x Z_4 are isomorphic as rings

bitter pilot
cobalt crypt
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yes

bitter pilot
cobalt crypt
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yes

bitter pilot
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Is there an explanation for that

cobalt crypt
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a unit of R x S is an element of R* x S*

bitter pilot
# cobalt crypt a unit of R x S is an element of R* x S*

Ok, so to understand it, Z_12* does not only denote the set of all integers mod 12 and g(x, 12) = 1 but it also denotes the set of all units of Z_12?
That being said Z_12* acts like a subset of Z_12. Same with Z_3* x Z_4* being a subset to Z_3 x Z_4.
If we consider them as rings (meaning we have both addition and multiplication), then it is clear that the structure in the units is therefore also persevered?

heady ibex
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Them being isomorphic is proven by proving an isomorphism exists

bitter pilot
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yea that's trivial

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i just wanted to get the intuition behind this

those in the know would just say that Z_12 and Z_3 x Z_4 are isomorphic as rings

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that this implies immediately that Z_12* and Z_3* x Z_4* are isomorphic

heady ibex
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You'd have to prove that the rings are isomorphic idk if that is any better

bitter pilot
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hmm ok

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In this exercise we explicitly considered them as groups actually not rings, so I am not quiet sure if I would be allowed to use Blake's argument but just for the sake of understanding, I think it makes sense

heady ibex
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So did you do it?

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Prove it?

bitter pilot
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I proved that there is an isomorphism between Z_12 and Z_3 x Z_4 previously

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as groups tho

heady ibex
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And now you have to do it for the multiplicative versions?

bitter pilot
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I did that too

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wait

bitter pilot
bitter pilot
heady ibex
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Mod is addition

bitter pilot
heady ibex
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Modulo is generally additive

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As in

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1 mod p is k * p + 1

bitter pilot
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4 mod p is k * p + 4

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(2 * 2) mod p is k * p + (2 * 2)

heady ibex
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Let p be 5

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Actually

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Not a prime

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8

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Then 2 * 4 is not an element of the multiplicative group if it is mod 8

bitter pilot
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It wouldn't be a group in the first place because it wouldn't be closed

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idk

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lmao

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😭

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1st task and it's been 3 hours already

signal pendant
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i believe this proof is fine to show isomorphism. what exactly is the problem you are having with it? the map is defined properly and is an isomorphism

bitter pilot
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I believe the proofs are fine (snow would otherwise say something) so I am gonna mark it as solved

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thanks to all! ❤️

#

.solved

vocal sleetBOT
#
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grizzled forge
vocal sleetBOT
grizzled forge
#

how do i do iii and iv)

half imp
#

What's the sum of all 5 roots

vocal sleetBOT
#

@grizzled forge Has your question been resolved?

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neon crypt
#

hello

vocal sleetBOT
neon crypt
#

I need help for this equation

loud walrus
#

!show

vocal sleetBOT
#

Show your work, and if possible, explain where you are stuck.

neon crypt
#

I have to use the gauss pivot, but how do I start is probably a simpler way to do

loud walrus
#

Your exercise looks wrong in the middle

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Your steps looks correct but idk what u wrote

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Step 2 and step 3 is what u have to do but the outcome is not correct

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@neon crypt

grim mason
#

hello

#

i got a question

loud walrus
#

L2 -> L2 -2L1 is equal to 0, 1/2, -2, -2

loud walrus
vocal sleetBOT
loud walrus
#

And L3-> L3-5L1 should be equal to 0, -3/4, 1, -7

vocal sleetBOT
#

@neon crypt Has your question been resolved?

neon crypt
loud walrus
#

2-2(3/4)=1/2

#

@neon crypt

neon crypt
#

okk i see thank you

#

i can continue

vocal sleetBOT
#
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tawdry stirrup
#

Does anyone have any advice for this task, because I haven't found anything similar on the internet. I simply can't find A and B after division, which is the remainder.

viral copper
#

See if you can write x^3 + 5x^2 - 12x + 3 in the form p(x^2 - 6x + 10)(ax + b) + c

heady ibex
#

wolfram says long division

vocal sleetBOT
#

@tawdry stirrup Has your question been resolved?

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vocal sleetBOT
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bitter pilot
#

Hi, can someone check the proof?

vocal sleetBOT
twin meteorBOT
#

𝔸dωn𝓲²s

hard atlas
#

how have you used that a,b are coprime

bitter pilot
#

I forgot it

hard atlas
#

its a very essential condition

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the problem is that the order of (1,1) is not always ab

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you need that they are coprime

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but here you just claimed it

bitter pilot
#

Z_2 x Z_2 = {(0,0), (0,1), (1,0), (1,1)}

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but gcd(2,2) = 2

tidal dock
twin meteorBOT
#

artemetra

bitter pilot
#

ok let me restart

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i confused something

bitter pilot
vocal sleetBOT
#

@bitter pilot Has your question been resolved?

bitter pilot
#

I don't know how to show that based on the fact gcd(a,b) = 1 it is ord(1,1) = ab

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ok for example

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k(1,1) = (0,0) then k = 0 mod a and k = 0 mod b so that would mean if k != 0 then the smallest next possible must be lcm(a,b)

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Axe

lilac pebble
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ye

bitter pilot
#

am I on the right track

lilac pebble
#

i was thinking along those lines, and
lcm(a,b) = |ab| / gcd(a,b)

inland galleon
bitter pilot
#

gcd(a,b) = 1 implies lcm(a,b) = ab

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😭

inland galleon
#

and you ended up proving something better

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the order of a general element in the product is lcm of the orders of the components.

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also before you get the wrong idea I've been helping you cause we played minecraft together, I've been helping anyone that I've seen from the server lol

bitter pilot
#

haha whaat

#

did i give you an elytra or something 😂?

inland galleon
#

indirectly I benefitted from one of your farms

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I think

bitter pilot
#

hmm ok

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well i basically helped Cyrenux, who built everything, on most projects, we even have a base together

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but cool lol

inland galleon
#

then yeah I definitely benefitted from the stuff you built, so this my way of saying thanks

bitter pilot
#

i see, thank you too

inland galleon
#

np

bitter pilot
#

thank you guys ❤️

#

.solved

vocal sleetBOT
#
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warm vector
#

I'm looking for some help on sports betting statistics. I currently have an app that gives as much info on each sports bet as it can (record, avg,etc). I show the win percent of bets which is just the record of that bet happening as well as a weighted chance of happeing which is this formula: a(1-b)/(a(1-b) + b(1-a)). This takes into account the other teams liklyhood of winning the bet as well which I like. So team A has an 80% chance of winning a game based on their record, playing team B that has a 40% chance of winning. We could assume that team A has a greater than 80% of winning because team B is not good, so the above formula would come out to 85.7% chance. I use this same formula for other bets such as spread and total. What I need help on is how can I use a formula like this that adjusts team A based on team B and use it for player bets. So if I have a player that has a bet of getting over X shots, their chance of that happening is 72%, but some teams average allowing less shots per game and some on average all more per game. How can I use this in a similar way as the formula above to calculate the adjusted number for a player?

vocal sleetBOT
#

@warm vector Has your question been resolved?

vocal sleetBOT
#

@warm vector Has your question been resolved?

vocal sleetBOT
#

@warm vector Has your question been resolved?

vocal sleetBOT
#
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hexed umbra
#

how am i supposed to find this

vocal sleetBOT
hexed umbra
#

tried this but didnt work

#

nvm i skipped it

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vast shale
#

Can I set this up as a proportion?
I did 27/63 =x/1.75
got 63x=47.25
Now x= .75
Point .75 of 36 is 27 which is the answer.
But I can’t work out in my head why it works.

vast shale
#

When I get .75, im confused on how to apply it back into the problem

half imp
#

The speeds are in a 4:3 ratio, so the times are in a 3:4 ratio

vast shale
half imp
#

so 3/7 is the proportion of the time the first trip took to the total

#

in other words the first trip took (3/7)*(1hr 45min) = 45 minutes

#

and the second trip takes 1 hour

#

the second trip is the easier one to calculate the distance for, of course

#

I think what you did works by pure coincidence and it wouldn't work if you changed the numbers

vast shale
half imp
#

Distance = 36*t1 = 27*t2

#

t1+t2 = 1.75

vast shale
vast shale
sick turtle
#

Yea it is system of equation

vast shale
#

.close

vocal sleetBOT
#

@vast shale Has your question been resolved?

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full fox
#

can anyone help me solve these derivatives using limit definition instead of the table? thats how the professor wants it
27 and 28

vocal sleetBOT
full fox
#

2

oak magnet
#

may we see what you've done so far ?

full fox
#

i tried this but idk if it leads anywhere

#

i have no clue how to get a h out and simplify

#

or should i multiply by 1/h and

#

idk man

full fox
#

27

vocal sleetBOT
#

@full fox Has your question been resolved?

full fox
#

<@&286206848099549185> ?

vocal sleetBOT
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@full fox Has your question been resolved?

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vocal sleetBOT
cursive turret
#

(a+b)^2=a^2+2ab+b^2

#

why do you beleive (2/5)^2?

#

its the same 3/4 -> 3/8

#

take the half as you have taken form 3/4 -> 3/8.

#

3/4 divided by 2 is 3/8. 2/5 divides by 2 is 1/5.

#

no. (a+b)^2 = a^2 + 2ab+b^2, so if oyu have something like x^2+2/5x and you wanna have a complete square like (a-b)^2 it means that 2/5x is 2 a b, so a = x and you hav to half the rest to get b.

#

the technique you wanna use is called "completing the square". you have a quadratic term like x^2+10x +3 you can write it as (x^2+10x + 25)-25+3 which gives you (x+5)^2-22

#

10x = 2ab, use a = x -> 10 = 2b -> b = 5

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vast shale
#

how to solve 2/3 power 2/3?

vocal sleetBOT
full hatch
#

Wdym with solve? It's not an equation. Do you mean compute?

vast shale
#

,w simplify (2/3)^(2/3)

twin meteorBOT
vocal sleetBOT
#

@vast shale Has your question been resolved?

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distant perch
vocal sleetBOT
distant perch
#

the first thing i did was multiply the first and last equation by two, but the book's answer decided to subtract the first from the last, if I subtracted the last from the first, the same answer would be achieved?

wind geyser
#

as long as the operation is valid i guess

mighty nacelle
#

there are many ways to solve systems of equations

#

the main thing is knowing that you got the right answer by plugging everything back in

#

if you have different methods and get the same (correct) answer, then it doesnt matter

distant perch
#

alright, because i added the first with the third and the last with the third, but i got a different answer at the end

#

So the problem probably isn't that, but something a did wrong later right

mighty nacelle
#

yeah probably

distant perch
#

alright then, thank you

#

have a great day

#

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sudden compass
#

yo

vocal sleetBOT
sudden compass
#

simple question

cyan talon
#

it's $\hat i$

twin meteorBOT
#

aPlatypus

sudden compass
#

oh thanks

#

okay yeah so 2 vectors

#

$A = a \hat i + b \hat j + c\hat k$ and $B = a' \hat i + b' \hat j + c' \hat k$ such that $a,b,c,a',b',c' \neq 0$

twin meteorBOT
#

rak³en

sudden compass
#

What does $A \cross B$ correspond to?

twin meteorBOT
#

rak³en

sudden compass
#

Like it makes sense for stuff like $6 \hat i \cross 7\hat j$

twin meteorBOT
#

rak³en

sudden compass
# twin meteor **rak³en**

but how do you a squeeze a third perpendicular vector out of this?? i'd love a diagram with an example, if someone has

woeful igloo
#

Two vectors make a plane

#

It has a perpendicular

sudden compass
#

not familiar with that concept

woeful igloo
#

Its euclids axiom. Two lines make a plane

sudden compass
#

ig its like how two sides make a closed plane in geometry?

woeful igloo
#

You can imagine the two vectors to be lines thru the origin

mighty nacelle
#

A X B is how much a vector "helps the other turn clockwise" so to speak

#

counterclockwise

sudden compass
mighty nacelle
#

i love conventions

sudden compass
#

ik how to find it bruh

mighty nacelle
#

so you want an intuition behind it?

sudden compass
cyan talon
# sudden compass hm?

they're talking about something like torque in mechanics I guess, which is a cross product

#

In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically

      τ
    
  

{\displaystyle {\boldsymbol {\tau }}}

, the lowercase Greek letter tau. When being referred to...

sudden compass
#

but yeah wait it makes sense to me now

#

if i treat the vectors as lines in 3D euclidian space

#

then the two lines will two planes

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and the line that is perpendicular to the plane

mighty nacelle
#

the two lines will make one plane

sudden compass
#

is the cross product (line version)

cyan talon
sudden compass
mighty nacelle
#

take two pencils

#

put their points togethert

sudden compass
#

thats exactly what I did 💀

mighty nacelle
#

they will lie flat on your desk

cyan talon
#

"after the point of intersection" what's that supposed to mean

sudden compass
#

like the pencils form an x right (u cant form a v with lines cus then they'd have to intersect at infinity)

#

so the upper portion is 1 plane, and the bottom portion is another right? or are they part of the same plane

cyan talon
#

what about the left and right portions too

mighty nacelle
#

both sides of the plane make one plane

cyan talon
#

now we have 4 planes devilish

sudden compass
cyan talon
#

yes

#

it extends in all directions not just "up" or "down"

mighty nacelle
#

its plane and simple

#

the right hand rule is a big helper in understanding what A does vs B

#

A stays in place and B does the turning

sudden compass
#

hmm makes sense

#

.close

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#
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left portal
vocal sleetBOT
left portal
#

Let $\mathbb{H}_1 = {\mathbf{x} \in \mathbb{R}^4 \mid x_1 - x_2 + x_3 - x_4 = 0}$, $\mathbb{H}_2 = {\mathbf{x} \in \mathbb{R}^4 \mid x_1 + x_3 = 0}$, and $\mathbb{S} = \langle (0, 1, 1, 2), (1, 1, 1, 0) \rangle$. Determine whether it is possible to find a projection $p: \mathbb{R}^4 \to \mathbb{R}^4$ such that $\text{Ker}(p) = \mathbb{S}$ and $p(\mathbb{H}_1) \subset \mathbb{H}_2$.

twin meteorBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

left portal
#

H1: x1-x2+x3-x4=0

x1=x2-x3+x4
(x1,x2,x3,x4)=(x2-x3+x4,x2,x3,x4)
x2(1,1,0,0)+x3(-1,0,1,0)+x4(1,0,0,1)
H1=<(1,1,0,0),(-1,0,1,0),(1,0,0,1)>

#

H2: x1+x3=0
x1=-x3
(x1,x2,x3,x4)=(-x3,x2,x3,x4)
x3(-1,0,1,0)+x2(0,1,0,0)+x4(0,0,0,1)
H2=<(-1,0,1,0),(0,1,0,0),(0,0,0,1)>

vocal sleetBOT
#

@left portal Has your question been resolved?

left portal
#

<@&286206848099549185>

#

the kernel and the image of a projection are in direct sum

left portal
#

<@&286206848099549185>

left portal
#

<@&286206848099549185>

cerulean drift
# left portal <@&286206848099549185>

there arent going to be many people who can help you with this problem i would try going to the math channel, but pinging continuously isnt gonna change much, sorry

blissful badge
cerulean drift
vocal sleetBOT
#

@left portal Has your question been resolved?

spiral turtle
#

Hi, one second

#

So I think that you can answer this question by answering the slightly easier question of "what is the dimension of the intersection of H1 and S?"

left portal
spiral turtle
#

If the answer to the above question is "1" then it should be possible to construct p.

#

If it is 2, then it is not

left portal
#

why

spiral turtle
#

Well, the kernel of p is the set of all vectors that get mapped to 0 by the transform

#

Wait

#

Hmmm.... No sorry, upon reflection the above may not be true, give me a moment to think

#

(not about the kernel obviously)

#

It should be possible regardless?

left portal
#

S = <(0,1,1,2),(1,1,1,0)>
s in S, a,b in R
s = a(0,1,1,2)+b(1,1,1,0)
s = (0,a,a,2a)+(b,b,b,0)
s = (b,a+b,a+b,2a)
(x1,x2,x3,x4)= (b,a+b,a+b,2a)
H1 : x1-x2+x3-x4=0
b-(a+b)+(a+b)-2a=0
b-a-b+a+b-2a=0
b(1-1+1)+a(-1+1-2)=0
b-2a=0
b=2a
(b,a+b,a+b,2a)=(2a,a+2a,a+2a,2a)
(2a,3a,3a,2a)=a(2,3,3,2)
H1 ∩ S = <(2,3,3,2)>

spiral turtle
#

Ok cool

#

So if we find H1 perp (H1 cap S), this is the basis set we need to map to somewhere in H2

#

We can construct this with a similarity transformation

twin meteorBOT
#

King Hassan
Compile Error! Click the errors reaction for more information.
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#

King Hassan
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spiral turtle
#

!nogpt

vocal sleetBOT
#

Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).

twin meteorBOT
#

King Hassan
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left portal
spiral turtle
#

Ok here's a way you can construct this

#

We do a similarity transformation

#

We have a change of basis matrix which contains {S, H1 perp (H1 cap S)} (as column vectors)

spiral turtle
#

Then we have a mapping matrix internally which is {0, 0, v1, v2} where v1 and v2 are destination vectors that map somewhere into the H2 subspace as expressed in this basis

#

If our change of basis matrix is D and our mapping matrix is Q then p is D Q D^(-1)

#

Note that the choice of v1 and v2 is not unique

#

We just need to make sure they are linearly independent

#

And not in S

left portal
#

H1 =<(1,1,0,0),(-1,0,1,0),(1,0,0,1)>
v = (x1,x2,x3,x4)

  1. v.(1,1,0,0)=0 <==> x1+x2=0
  2. -x1+x3=0
  3. x1 + x4=0
    x1 = x1
    x2 = -x1
    x3 = x1
    x4 = -x1
    H1 perp = <(1,-1,1,-1)>
spiral turtle
#

By H1 perp (H1 cap S) I mean the portion of H1 that is perpendicular to the intersection of H1 and S

#

Though I guess it's more simply expressed as H1 perp S

left portal
#

so the intersection between H1 and the orthogonal complement of H1 ∩ S

spiral turtle
#

Yes exactly.

#

To find v1 and v2 you'll want to also find the same thing, but for H2 and S

#

(and then feed it through the change of basis matrix)

#

But before you get to number crunching, does it at least make conceptual sense?

#

I'd like you to double check my work

#

Just to make sure I haven't made a mistake and we're on the same page

left portal
#

H1 ∩ S = <(2,3,3,2)>
v . (2,3,3,2)=0
2x1+3x2+3x3+2x4=0
2x1 = -3x2-3x3-2x4
x1 = (-3/2)x2 + (-3/2)x3 - x4
(x1,x2,x3,x4)=((-3/2)x2 + (-3/2)x3 - x4, x2,x3,x4)

x2((-3/2),1,0,0) + x3((-3/2),0,1,0) + x4(-1,0,0,1)

so the orthogonal complement of
H1 ∩ S is <(-3/2),1,0,0),(-3/2),0,1,0),(-1,0,0,1)>
=<(-3,2,0,0),(-3,0,2,0),(-1,0,0,1)>

blissful badge
#

You can check mine also, if it's shown to you.

spiral turtle
#

@left portal as mentioned it will probably be less work overall to find the orthogonal complement of S instead.

#

Because H1 perp (H1 cap S) = H1 perp S. And because you'll need to also calculate H2 perp (H2 cap S) = H2 perp S

#

So if you have the orthogonal complement of S you can simply reuse it later

#

(In long and complicated problems it is generally beneficial to make a "roadmap" of the solution, so that you can try to minimize the amount of work you need to do by hand. This is one example where it saves a little bit of effort.)

left portal
#

H1 cap S I can understand why we look for that

#

H1 is part of the preimages of p same with S, it's part of the preimages of p

#

the dimension of H1 cap S has to be >= 1 otherwise is impossible to define a projector p such that the conditions hold

there is a property that to uniquely define a linear transformation, and thus, a projection operator

we need to define it wrt to a basis

spiral turtle
#

Well, the dimension of H1 cap S must be >= 1 by virtue of being in R^4

#

Because dim(H1)=3 and dim(S)=2

left portal
#

ye and R5 is bigger than the domain R4

#

we found H1 cap S, I got a bit lost with the change of basis approach and the orthogonal complements tbh

spiral turtle
#

That's fair!

#

Ok so, we want p to have a kernel equal to S

#

So that will mean that in your theorem above, two of the v_i will be a basis for S

#

And they map to the 0 vector because kernel

#

And the other two will need to be in H1 but not in S

#

And will need to map somewhere into H2

#

I guess I was wrong though, anywhere into H2 works, doesn't matter if it's in S or not

left portal
#

problem is H1 is dim(3)

spiral turtle
#

Not a problem

#

Because the space of vectors in H1 but not in S is dim 2

left portal
#

the real problem then is H2 is dim 3

#

S=<s1,s2>
H1 but not in S = <v1,v2>
p(s1)=0
p(s2)=0
p(v1) = ?
p(v2) = ?

spiral turtle
#

Also not a problem.

#

We can just choose two vectors in H2

#

The choice isn't unique

#

But the problem doesn't specify it has to be

#

We can just pick 2 of the 3 basis vectors

left portal
#

what is the subspace H1 but not in S?

H1 ∩ S perp

spiral turtle
#

Yeah $H_1 \cap S^{\perp}$

twin meteorBOT
#

OmnipotentEntity

spiral turtle
#

Which I've been writing as H1 perp S as a sort of shorthand.

left portal
#

ok, let me find the orthogonal complement of S

S = <(0,1,1,2),(1,1,1,0)>
v = (x1,x2,x3,x4)
v . (0,1,1,2) = 0 <==> x2+x3+2x4=0
v . (1,1,1,0) = 0 <==> x1 + x2 + x3 =0
i) x2 = -x3 - 2x4
ii) x1 = -x2 - x3
x1 = x3 + 2x4 - x3 ==> x1 = 2x4
x2 = -x3 -2x4
(x1,x2,x3,x4)=(2x4,-x3-2x4,x3,x4)
x4(2,-2,0,1) + x3(0,-1,1,0)
S perp = <(2,-2,0,1),(0,-1,1,0)>

v in S perp
a,b in R

v = a(2,-2,0,1)+b(0,-1,1,0)
v = (2a,-2a-b,b,a)

equation of plane H1
x1-x2+x3-x4=0
2a-(-2a-b)+b-a=0
2a+2a+b+b-a=0
3a+2b=0
a = (-2/3)b

(2a,-2a-b,b,a) = ( 2(-2/3)b, -2(-2/3)b - (3/3)b, b , (-2/3)b )
b( -4/3, 1/3, 1, -2/3)
H1 ∩ S perp = <(-4/3, 1/3, 1, -2/3)>
=<(-4,1,3,-2)>

left portal
spiral turtle
#

Well, you found H1 cap S, and it was dim 1, right?

spiral turtle
#

If H1 is dim(3) it would stand to reason that H1 cap S perp is dim(2)

#

Because (H1 cap S) cup (H1 cap S perp) = H1

left portal
#

Hmm oh my

#

I found the orthogonal complement of S correctly it seems because

S + S perp = R^4

spiral turtle
#

Excellent

left portal
#

but maybe I messed up the intersection

spiral turtle
#

Maybe double check both intersections?

left portal
#

ye let me bring pen and paper

#

So it's faster than typing on my phone

twin meteorBOT
left portal
#

Still dim 1

vestal bane
#

🍎🍎

spiral turtle
#

@left portal sorry, give me a second, I went AFK

#

I'll work this problem now and compare notes afterwards

vocal sleetBOT
#

@left portal Has your question been resolved?

left portal
#

Sometimes I think profesor doesn't want us to pass, but I will manage somehow, someway, I study a lot

spiral turtle
#

I'm still working through the problem.

#

@left portal

#

The dimension of H1 cap S perp is definitely 1.

#

it's the subspace sum of the two that is 3 dimensional.

left portal
#

Ye A union B is most of the cases never a subspace because it's not closed under addition

#

Usually A + B is more appropriate

#

,, \cup

twin meteorBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

spiral turtle
#

yeah

#

So ok

#

we can just select v1 to be the basis of H1 cap S perp, (4, -1, -3, 2). And then v2 is some linear combination of the basis of H1 cap S perp and H1 cap S, I just chose (1, 1): which gives (6, 2, 0, 4)

#

these two vectors are in H1, but not in H1 cap S.

#

and they are linearly independent.

#

so we have our two vectors we map into H2.

#

Your work was correct btw.

#

Or at least it matches mine

#

Ignore the bit at the very top, a different problem.

left portal
#

Some linear combination of the basis of H cap Sperp and H cap S

#

?

spiral turtle
#

yeah, as in, we just want some vector off of H1 cap S

#

so a (non-zero) linear combination of these two spaces suffices.

left portal
#

Also H2 = H i pressume

spiral turtle
#

where?

#

oh, H1 in this case

left portal
#

Ok

spiral turtle
#

Edited.

left portal
#

S=<s1,s2>
H1 cap S perp = <v1,v2>
p(s1)=0
p(s2)=0
p(v1) = ?
p(v2) = ?

spiral turtle
#

p(v1) = a basis for H2
p(v2) = a different basis for H2

#

i guess they don't have to be different, or even bases, just two vectors in H2.

spiral turtle
#

wait no, they do have to be linearly independent

#

because we know the kernel of p.

left portal
#

Elaborate

spiral turtle
#

So if they were linearly dependent, then the kernel of p would be larger,

#

but yeah, any two linearly independent vectors in H2

#

it's easy enough to just choose two of the bases.

left portal
#

H2: x1+x3=0
x1=-x3
(x1,x2,x3,x4)=(-x3,x2,x3,x4)
x3(-1,0,1,0)+x2(0,1,0,0)+x4(0,0,0,1)
H2=<(-1,0,1,0),(0,1,0,0),(0,0,0,1)>

spiral turtle
#

bases being the plural of basis

#

pronounced "bay-seeze"

left portal
#

Basis vector

spiral turtle
#

we can choose (-1, 0, 1, 0) and (0, 1, 0, 0), or we can choose (0, 1, 0, 0) and (0, 0, 0, 1), etc.

#

a basis vector can be called a basis for short. And then I pluralized it to "bases" which pluralizes like that because it's a greek derived word ending in "sis"

left portal
#

S=<s1,s2>
H1 cap S perp = <v1,v2>
H2 = <v3,v4,v5>
p(s1)=0
p(s2)=0
p(v1) = v3
p(v2) = v4

spiral turtle
#

well, not quite

#

S=<s1,s2>
H1 cap S = <v1>
H1 cap S perp = <v2>
H2 = <v3,v4,v5>
p(s1)=0
p(s2)=0
p(v1 + v2) = v3
p(v2) = v4

left portal
#

x = v1+v2

Is x linearly independent to v2?

#

Because

#

We need to define it on a basis of R4

#

If {s1,s2,v1+v2,v2} forms a basis of dim 4 then it's fine

spiral turtle
#

x and v2 are independent, because if we let ax + bv2 = 0, then we have a(v1 + v2) + bv2 = 0, giving a = -b and a = 0 as the requirements for the solution

#

which gives the only solution at (0, 0)

#

oh, good point.

#

I don't think the entire collection is linearly independent.

left portal
#

p : R4 -> R4

spiral turtle
#

I guess we need to adjoin v2 with a basis of H1 linearly independent to it and not in S.

#

rather than with v1.

#

we have (1, 1, 0, 0) which is linearly indepenent of (4, -1, -3, 2) and S.

#

which is just the first basis vector of H that I have in my set.

left portal
#

Okay good

spiral turtle
#

so {s1, s2, h11, v2} should be linearly indepedent, but let's double check just to make sure.

#

I'll use a computer for this though

left portal
#

(1,1,0,0) is in H1 and linearly independent to S and linearly independent from the vector of Sperp cap H1

left portal
spiral turtle
#

So the determinant of the above matrix is -12, so we're good!

left portal
#

Good

#

As long is not zero

spiral turtle
#

so honestly, this is done, you've proven that there exists a linear transform satisfying the problem

#

And it doesn't say to find the linear transform

left portal
#

The original exercise says find a projection such that

#

Is just that i wrongly translated

spiral turtle
#

fair enough!

#

ok so, then we just need to do the similarity transform

spiral turtle
#

our mapping matrix is going to be {0, 0, v3, v4}

left portal
#

H1=<(1,1,0,0),(-1,0,1,0),(1,0,0,1)>
S=<(0,1,1,2),(1,1,1,0)>

spiral turtle
#

and D is {s1, s2, h11, v2}

#

so now you just have some troublesome calculations ahead.

#

involving inverting D and then doing a couple of matrix multiplications

#

and then double checking your result.

left portal
#

H1 cap S perp =<(4,-1,-3,2)>

spiral turtle
#

that's what I got

#

I think that's what you got as well

left portal
#

p(0,1,1,2)=0
p(1,1,1,0)=0
p(1,1,0,0) = (-1,0,1,0)
p(4,-1,-3,2) = (0,1,0,0)

#

Should be the projection

#

Ker(p) ⊕ Im(p) = R^4 aswell

left portal
#

We can find the p(x1,x2,x3,x4) = something
With some couple extra steps tho

#

Let me give an example

#

In the example 5

spiral turtle
#

ah, fair enough

#

well, let's finish it and check our work to make sure it's fine

twin meteorBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

spiral turtle
#

oh, thanks for the translation

left portal
#

Is just using linearity

#

Scalar out and separate the sums

spiral turtle
#

yeah, I gathered 🙂

#

but nevertheless I appreciate the translation

left portal
#

No problem :') you have helped me a ton

left portal
spiral turtle
#

jfyi, it's doing the exact same thing I did above just with a handful more steps

#

I'm getting:

#

[
\frac1{6}
\begin{bmatrix}
2 & 4 & -6 & 1 \
-4 & 10 & -6 & -2 \
-6 & 12 & -6 & -3 \
0 & 0 & 0 & 0
\end{bmatrix}
]

twin meteorBOT
#

OmnipotentEntity

spiral turtle
#

It maps S to 0, as required, but it doesn't map H1 to H2, I'm getting that for any vector (a, b, c) written in the basis of H1, it maps to (a -4b/3 + c/2, a - b/3 - c, a - 3c/2, 0)

#

which is only in H2 sometimes.

#

specifically when b = 3c/2

#

which means we've made a mistake regarding the whole perp S stuff

#

maybe we need only find a basis of H1 that includes one vector in S?

#

(and map that vector to 0)

left portal
#

Basis for H1 cap S is <(2,3,3,2)>

spiral turtle
#

So we have
p(0, 1, 1, 2) = 0
p(2, 3, 3, 2) = 0

#

and now we need two more vectors in H1 that are linearly independent of (2, 3, 3, 2)

#

we can select two of the bases, probably

left portal
#

H meaning H1

#

H1=<(1,1,0,0),(-1,0,1,0),(1,0,0,1)>

spiral turtle
#

p(1, 1, 0, 0) = (-1, 0, 1, 0),
p(1, 0, 0, 1) = (0, 1, 0, 0)

#

let's check to make sure our vectors are linearly independent

#

they are

left portal
#

,w det {{1,1,0,0},{1,0,0,1},{0,1,1,2},{2,3,3,2}}

twin meteorBOT
spiral turtle
#

still no good

#

H1 is being mapped outside of H2

left portal
#

Its tricky to work with projections, there are some properties i didn't mentioned

#

Like p(v)=v if v in Im(p)

spiral turtle
#

ah, so you're saying that we need to find two vectors in H1, not in S and not in H2?

left portal
#

H being H1

spiral turtle
#

I keep doing it, sorry

#

hmm... but the three I selected satisfy that

left portal
#

Nah if they are in H1 they should be mapped to vectors contained in H2, p(H1) should map to vectors in H2

spiral turtle
#

The above I definitely did

#

sorry, my dumb that final line should be a plus rather than a minus

#

but it's still non-zero

#

oh good lord

#

I'm a moron, I know what I'm doing wrong.

left portal
#

what happened

#

is that mathematica

#

this is the solution, but is in spanish let me translate that

spiral turtle
#

There, I was missing a key step

#

I needed to change the mapping matrix to be relative to the basis of H1

#

There's probably a less yick way to do this on the mathematica side.

#

but it works

twin meteorBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

left portal
#

why are they doing H1 n H2

left portal
# spiral turtle

we prolly defined a linear transformation correctly but since is a projection, is prolly tricky with the image

spiral turtle
#

oh, ok, that works too

#

I completely missed the fact that p was supposed to be a projection all of this time

#

I thought it was merely supposed to be a general linear transformation.

#

ok ok ok

#

the reason why they do H1 cap H2 is because if the vector is already in H2 (and not in S) we don't want the vector to change.

#

it's the definition of a projection.

#

so we need to find the set of all vectors where this is the case.

#

and those are the intersection

#

I feel like a moron now.

#

anyway

left portal
#

you are good, this is real good practice

#

most people are never taught linear transformations like that

spiral turtle
#

it's honestly why I help.

#

learn new ways of approaching things, and keep myself sharp

left portal
#

I appreciate the help, we did a lott

#

like i also have to do the same for linear transformations and with projections

#

so is good practice still, but now that I look at the solution, projections are a bit easier

#

because p(v) = v if v in Im(p)

left portal
spiral turtle
#

yeah exactly 🙂

left portal
#

I cannot thank you enough though, everyone ignored me, I really appreciate it omni

spiral turtle
#

it's not that everyone ignored you, it's just a large commitment to help with a problem like this, and there are a smaller than average number of users who can

#

The other guy just shat some chatgpt garbage at you, which honestly I think is infinitely worse

#

anyway, yo, glad we got this sorted.

#

sorry for leading you down a false path because I misunderstood the question at a basic level :x

left portal
# spiral turtle learn new ways of approaching things, and keep myself sharp

You are really smart, and you are a wonderful helper Omni, I appreciate it, I know it was a big commitment to help, but people also were reluctant to help in lin alg channel, I wan to be like that when I grow older, when you get older you stop learning and who that stops learning stops living. I appreciate it, we practiced linear maps aswell, thank you so much for taking the time

spiral turtle
#

You're very welcome

left portal
#

.solved

vocal sleetBOT
#
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vocal sleetBOT
#
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vast shale
#

Whoever can solve (b) shall get 1:1 succ

vocal sleetBOT
strong vortex
hushed pewter
vocal sleetBOT
hushed pewter
#

also don't be gross

vast shale
#

o wait

#

i forgot to post my progres soz

#

I've plateud right here

#

ignore strat on the right side

#

what if the question is broken

#

Build Decision Tree using Gini Index Solved Numerical Example Machine Learning by Dr. Mahesh Huddar

In this video, I will discuss, how to build a decision tree using the Gini index for the given data set. The data set has 3 attributes weather, parent, and money. The output variable has the following possibilities - Cinema, Stay In, Tennis, Shop...

▶ Play video
#

Just try harder bro!

#

Oh my heckin science is this it? Is person 3# undeterminable? And that's why d is 50%

vocal sleetBOT
#

@vast shale Has your question been resolved?

vocal sleetBOT
#
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vocal sleetBOT
#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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shy sleet
#

Can someone show me how to draw this?

vocal sleetBOT
hushed pewter
shy sleet
#

Done

hushed pewter
#

Draw a random point anywhere (except at T), and label it K

shy sleet
#

Ok done

hushed pewter
#

Draw the straight line KT. It will intersect with circle (twice). Mark a point at either intersection at label it Y

shy sleet
#

Does it matter if its the first intersection

#

Or second

hushed pewter
#

oh hol up

#

one thing

#

It says that K will have a tangent to the circle, which means that the point K must be outside of the circle

shy sleet
#

Ok i did it ouside

hushed pewter
#

good

#

Then now just draw the line segment KT

shy sleet
#

Done

hushed pewter
#

the segment KT will intersect the circle at just a single point now. Mark that intersection and label it Y

shy sleet
#

The first or second intersection

hushed pewter
#

there should be only one in the segment KT (not the infinite line)

shy sleet
#

Oh ok

#

Done

#

I think thats all

hushed pewter
#

You also need to draw a line that goes through K and is tangent to your circle

#

there are two possible lines that could be drawn, but you only need to choose one

shy sleet
#

Something like this?

hushed pewter
#

No. That line is not tangent to your cirlce

hushed pewter
#

yeh

#

close enough

#

I know what you are going for

shy sleet
#

And the line only goes to the point of tangency?

#

And I find that

hushed pewter
#

yes

shy sleet
#

Dont we just use pythagorean

#

To find that side

hushed pewter
#

yes

shy sleet
#

Ok thanks

#

.close

vocal sleetBOT
#
Channel closed

Closed by @shy sleet

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#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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bitter pilot
#

Hello

vocal sleetBOT
bitter pilot
#

Can somebody check my proof?

twin meteorBOT
#

𝔸dωn𝓲²s

cedar burrow
cedar burrow
bitter pilot
#

what do you mean one n?

cedar burrow
#

Since the assumption holds for all n, it in particular holds for some particular n

bitter pilot
#

Oh bruh

#

For n = 1 ax = 1 too

cedar burrow
#

Yep

bitter pilot
#

hence a is also unit

#

i am physically not well

#

thanks

cedar burrow
#

a^1 in R is the same as a in R

bitter pilot
#

yes

#

Yea having x^(n^-1) = x^(1/n) is questionable right

cedar burrow
#

I also see you’re up quite late (not that I’m any better)

bitter pilot
#

yea

#

honestly i am amazed how I struggled with the <= more than =>

#

anyway thanks again!

cedar burrow
#

No problem

bitter pilot
#

happy new year

#

soon

cedar burrow
#

Yeah in 21 hours and a bit

#

Guten Rutsch

bitter pilot
#

Dir auch!

#

.solved

vocal sleetBOT
#
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vocal sleetBOT
#
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west coyote
#

is my answer correct for this question?

vocal sleetBOT
west coyote
#

here's my answer:

bitter pilot
west coyote
# bitter pilot seems about right

I made the whole graph +1 up to simply integrate it with respect to x but also converse the distance of revolving radius. That's correct approach right?

bitter pilot
#

that's also a way to interpret it geometrically

#

or rather approach the problem

west coyote
#

how do they solve it without geometrically shifting it?

#

is there another formula or something?

bitter pilot
#

there exists the shell method too but that requires a change of variables

west coyote
#

ah okay. I will check that. Thanks

#

.close

vocal sleetBOT
#
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vocal sleetBOT
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vocal sleetBOT
#
Channel closed

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snow knot
#

Anyone knows how to do just question a as an example? I don’t really know how to do it in word form like is it all real numbers greater than -6 smth like that?

sullen shoal
#

Alright so I think I understood

#

Ok so consider 2a)

#

Do u know how to write line equation?

#

Oh nvm they didn't ask for equation

#

So basically if u see the graph for a)

#

x starts at what and ends at what

snow knot
#

3 and -6?

sullen shoal
#

Ah nop

#

Ok so

#

If u have arrows

#

It means it is a line i.e., goes all the way from -infinity to infinity

#

If u have 1 dot and 1 arrow, it is a ray

#

If u have 2 dots then it means u have a line segment, which is a small part of the line

#

So now say

tulip nebula
#

x means the point corresponding to line on x axis

sullen shoal
#

@snow knot

snow knot
sullen shoal
#

Yepp

#

So for a)

#

x value varies from -infinity to infinity

#

So u denote it as x€R

snow knot
#

Y is the same? Or is it different

sullen shoal
#

Consider that C has only 1 line the middle (it means belongs)

sullen shoal
snow knot
#

Kk, I think I’ve got it, thanks :)

sullen shoal
#

Anytime!

snow knot
#

I type .close right?

sullen shoal
#

Yep

snow knot
#

Kk catthumbsup

#

.close

vocal sleetBOT
#
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vocal sleetBOT
#
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shy otter
vocal sleetBOT
shy otter
#

how to start

peak matrix
#

$\left(\left(2^{-2^{x-1}}\right)^{4}+2^{-2^{x-1}}\right)^{2^{-x}}$ it's the same thing as this I think

twin meteorBOT
#

MæthIsAlwaysRight

peak matrix
#

$\left(\frac{\left(2^{-2^{x-1}}\right)^{3}+1}{2^{2^{x-1}}}\right)^{2^{-x}}$ which is same thing as this

twin meteorBOT
#

MæthIsAlwaysRight

shy otter
#

?

#

where did 4 come from

peak matrix
#

4 = 2^2

#

-2^(x+1) = -2^(x-1) * 2^2= -2^(x-1) * 4

scenic ravine
shy otter
#

how do u know

scenic ravine
#

Oh, I sort of prepared for the exam

shy otter
#

how do u solve this though

scenic ravine
#

and then make a substitution to simplify the probelm

peak matrix
#

$\frac{1}{\sqrt{2}}\left(\left(2^{-2^{x-1}}\right)^{3}+1\right)^{2^{-x}}$

twin meteorBOT
#

MæthIsAlwaysRight