#help-43

1 messages · Page 56 of 1

random mica
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ok

heady spruce
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im kinda confused

random mica
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so AD is the angle bisector

heady spruce
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yea

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angle BAD = andle CAD

random mica
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correct

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we are given that B > C

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now look at the other angles

heady spruce
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hmm

random mica
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is angle ADC bigger or smaller than ABD

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(hint sum of 2 opposite interior angles = exterior angle)

heady spruce
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bigger

random mica
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Yes, as ADC = ABD + BAD

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so ADC > ABD = B

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but we know B is greater than C

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so ADC > C

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so what can you conclude about the side inequalities for triangle ADC

heady spruce
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wait

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wym

random mica
heady spruce
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the ADC>C part

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waht is c

random mica
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sorry its the shorthand they used

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angle C

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basically angle ACD

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should I explain again

heady spruce
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no need

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so in ADC

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AD>CD

random mica
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uhm not quite

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whats the side opposite to angle ADC

heady spruce
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AC

random mica
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yes and whats the side opposite to angle C

heady spruce
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AD

random mica
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yes so AC > AD

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right?

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and thats one of the options

heady spruce
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oh ye

random mica
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what else can we definitely conclude

heady spruce
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CD>BD

random mica
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yes but why

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its the angle bisector ratio right?

heady spruce
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ye

random mica
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BD/CD = AB/AC

heady spruce
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im preety sure that is it

random mica
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yes

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the other ones cant be properly concluded

heady spruce
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trye

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true*

random mica
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you can play around with moving the point A in your head

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and see how AD changes

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or in geogebra

heady spruce
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ok

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tysm btw

random mica
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welcome

heady spruce
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.close

compact pewterBOT
#
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compact pewterBOT
#
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vernal jacinth
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hi

compact pewterBOT
vernal jacinth
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this question is wrong, right ?

kind viper
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why so

kind viper
vernal jacinth
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we dunno the exact value of lix x to 1

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-2 as well

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soo ?

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this one is also wrong , right ?

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hey guys ... pls help

feral flicker
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Who made these questions? 🤯

vernal jacinth
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dunno

vernal jacinth
feral flicker
#

I think they don't contain enough information to answer them. The latter question has a problem at x=1 where it is discontinuous and therefore does not exist. You would have to stipulate if the limit is coming from one direction or the other.

vernal jacinth
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plus we dunno the value at f(0)

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thats also a problem i guess

feral flicker
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You can infer that all the values at x=0, lim x->2 f(x), and lim x->1^+ f(x) are the same.

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And that's where the lack of information comes into play.

vernal jacinth
feral flicker
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It doesn't even show f(x) at x=-2.

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Perhaps they meant x->2.

vernal jacinth
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🙁

feral flicker
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These questions are not written well.

surreal shard
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u need to take into account that the slope is constant

vernal jacinth
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but can we infer that for x = -2 it will be -1

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i mean , we dont see that part of the function

vernal jacinth
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isnt it ?

vernal jacinth
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at x = k answer is 0

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at x = 0 and x = 2 answers are the same

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soo 2l = 4

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l = 2

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f(0) = 2

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and if we make the equation of line then k is -2

compact pewterBOT
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@vernal jacinth Has your question been resolved?

vernal jacinth
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.CLOSE

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compact pewterBOT
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delicate pulsar
#

Need help with number 13

compact pewterBOT
vague sparrow
#

I can't see. Maybe take it clearly

delicate pulsar
# vague sparrow I can't see. Maybe take it clearly

As part of Kayla's exercise program, she either runs 6 miles/day or rides her bike 10 miles/day. Her new goal is to cover a minimum distance of 200 miles, with at least 15 of the days running. She would like to determine the number of days it would take to accomplish this.

vague sparrow
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so we're using the x y coordinate

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right

delicate pulsar
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i made the equations x>_ 15
and
6x+10y >_ 200

delicate pulsar
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idk what to do now

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but i decided to make y=mx+B out of the 6x+10y equation

vague sparrow
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alright so we know that the slope of the line is $\frac {y_2 - y_1}{x_2 - x_1}$

boreal girderBOT
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Average_X^2

delicate pulsar
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i mean systems of linear inequalities

vague sparrow
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so we're using $y = mx + b$

boreal girderBOT
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Average_X^2

delicate pulsar
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heres the equations i made out of the word problem:

6x+10y > 200
x > 15

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turn it into y + mx+b ill end up with

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y> -3/5x + 20
x>15

vague sparrow
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ok

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so its $y> = -3/5x + 20.$ where b is 20.

boreal girderBOT
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Average_X^2

delicate pulsar
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b is 20

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i just dont knows how to graph the -3/5

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(its not a full graph)

vague sparrow
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alright so,

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Lets see if we can graph $-3, -5$

boreal girderBOT
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Average_X^2

vague sparrow
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will that work?

delicate pulsar
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yeah

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Also this is the graph they gave me

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@vague sparrow

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oh wait now i get how to graph

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alr im good now

compact pewterBOT
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@delicate pulsar Has your question been resolved?

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grizzled geyser
#

I'm wondering whether a set $X \subseteq R^k$ can be both open, closed and bounded. I think it should be impossible. My attempted proof is as follows. $X$ is bounded, so take $q \in X$. Let $h = inf{d(p,q) | p \in X^{\text{c}}}$. There are two possibilities:

If there is a point $p \in X^{\text{c}}$ such that $d(p,q)=h$, then $p$ is a limit point (otherwise, there is a neighborhood $N_p$ such that $N_p \cap X = \emptyset$. Taking a $r \in N_p$ between $p$ and $q$ produces a point with shorter distance to $q$ than $p$, which is a contradiction). Thus $p$ must be an element of $X$ because $X$ is closed, violating the construction of $p$

But, I'm stuck on the case that there is no such point. I think there should be a point, since $X$ is open.

boreal girderBOT
untold cairn
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There are exactly two subsets of R^k that are both open and closed: the empty set and R^k itself. This is because R^k is connected

south sage
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Well if it's closed and bounded it's compact which means that it can't be open

untold cairn
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There are some topological spaces where some non-empty sets are both compact and open though. The reason you can't in R^k is basically because R^k is connected I think

compact pewterBOT
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@grizzled geyser Has your question been resolved?

grizzled geyser
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Wait, give me time to think

grizzled geyser
trim isle
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no

untold cairn
grizzled geyser
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Okay, I found the proof here. Thanks.

#

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compact pewterBOT
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compact pewterBOT
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cerulean thorn
#

yes and whats the side opposite to angle C

compact pewterBOT
compact pewterBOT
# cerulean thorn yes and whats the side opposite to angle C

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

proven wren
bleak dock
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mods are aware of it

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.close

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ionic ermine
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when will PA.PB be minimum? Any concept here that I'm not aware of?

compact fractal
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does PA.PB mean PA * PB

ionic ermine
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yea

compact pewterBOT
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@ionic ermine Has your question been resolved?

ionic ermine
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i guess I'll ask a bit later, try and see if you find something

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open plaza
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.reopen

compact pewterBOT
open plaza
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@ionic ermine is trig allowed

ionic ermine
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yea sure

open plaza
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here's our figure

cursive harbor
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Wait why does the question give you P

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I just noticed that

open plaza
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P is already given

cursive harbor
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Yeah why lol

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Oh nvm A and B are not

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I'm dumb sorry

open plaza
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so from sine theorem, PA = PO*sin(POA)/sin(A)

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likewise for PB

ionic ermine
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ok

open plaza
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and because PA.PB needs to be the minimum, sin(A).sin(B) needs to be the maximum

ionic ermine
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but

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POA and POB also vary

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ok

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yea i see

open plaza
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$sin(A) \cdot sin(B)$ can be rewritten as $\frac{1}{2} \cdot [cos(A-B) - cos (A+B)]$

boreal girderBOT
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(De)Carbonized

tiny prawn
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What is this channel for

open plaza
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@ionic ermine this should be enough hints I suppose

ionic ermine
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yea

open plaza
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there are prob easier approaches

ionic ermine
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really good idea though that the lines can be seen as origin and thier angles

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compact pewterBOT
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compact pewterBOT
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old flame
#

simple Algebra II question, working on a practice assignment.
I've been trying to figure out a step in the factoring of this polynomial,
How does x^2 - x + 6 turn into (x^2 + 2x) + (-3x - 6), where do the 2x and -3x come from?

mild sky
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2x-3x = -x

old flame
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okay gimme a second

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where do you get that from

south kindle
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...

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We turn -x into 2x-3x

old flame
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based on...

south kindle
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To factories it

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Ize

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Ex nihilo

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Idk whats the word in english

topaz cargo
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Educated guess based on Vieta's

south kindle
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無中生有。

old flame
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confused

south kindle
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Its hard to explain ;-; its just u need to change stuff based on what u have

old flame
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i have the knowledge base of an american hs junior

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lol

old flame
topaz cargo
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Vieta's theorem

old flame
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alright let me look into that

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wasnt covered by name

south kindle
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.

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Do you have a calculator

old flame
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yes

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im just struggling with theory here

south kindle
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You can do it with cross method or

old flame
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so you just find this by plotting it

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is that the simplest solution

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oh im an idiot

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alright thank you

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.close

compact pewterBOT
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compact pewterBOT
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old flame
#

How would I properly write the linear factors of (x^2 -4) (x^2 -9)

mild sky
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Do you know how to factor x^2-4 and x^2-9

old flame
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yes but my practice assignments answer checker is saying its wrong

mild sky
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What was your result

wooden slate
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the expansion using algebraic identity a^2 - b^2 was wrong?

old flame
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give me a second to type it out

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(x + 2) (x - 2) (x+ 4.5) (x- 4.5)

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did i misplace a negative

mild sky
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4.5?

old flame
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oh man

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would it not be 9/2

strange ermine
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Nope, what formula are you using?

old flame
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well there it is

mild sky
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You are using

old flame
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oh its the square not the half

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boy am i dumb

strange ermine
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Square root, not square

old flame
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ykwim

kind viper
old flame
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alr

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mb

mild sky
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Accuracy is important

kind viper
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if you must shorten it to one word then say root

old flame
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i was doing it backwards in my head when i said it

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mistake

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anyway

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.close

compact pewterBOT
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compact pewterBOT
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wispy warren
#

please check if the range is correct

compact pewterBOT
viscid shard
#

why is positive 1 excluded from the range?

wispy warren
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because it doesnt include it from -x wherein x is between 0 and 1?

balmy dawn
#

It should be included.

wispy warren
#

I think I got it now

viscid shard
wispy warren
#

so I should base on the cases that it does?

viscid shard
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yes, because it is indeed possible for f(x) to be equal to 1

wispy warren
#

okay thank you

#

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compact pewterBOT
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wispy warren
#

@viscid shard uhm wait is the domain correct tho does it affec

wispy warren
#

since theres a hole in 0 shoud I also restrict it in my domain?

compact pewterBOT
wispy warren
#

I forgot to ask this

viscid shard
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but let's see

wispy warren
#

oh sorry

grizzled geyser
#

$x \leq 7$?

boreal girderBOT
viscid shard
#

I don't see anything wrong with the domain as written, but what's that at the top?

viscid shard
#

(as in the line pointed out by Xwtek)

wispy warren
#

thats 1

grizzled geyser
#

That still doesn't make sense since it overlaps with second, third, and fourth condition.

viscid shard
#

you mean **-**1?

wispy warren
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oh sorry its -1

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sorry its a mess when I write

viscid shard
#

it's fine. so what's the issue again?

wispy warren
#

my question basically is or does the restriction of range affect the domain or its independent of it

viscid shard
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independent of it

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I mean, you can have f(x) = 5 for all real x

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the domain is still (-infty, infty)

wispy warren
#

oh okay thank you, and sorry for pinging u

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foggy wing
#

2/x+3=-1/x

compact pewterBOT
keen granite
chilly basalt
#

$\frac{2}{x} + 3 = -\frac{1}{x}$

boreal girderBOT
#

e4 e5 Qh5 Nc6 Bc4 Nf6 Qxf7#

chilly basalt
#

or

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$\frac{2}{x+3}= -\frac{1}{x}$

boreal girderBOT
#

e4 e5 Qh5 Nc6 Bc4 Nf6 Qxf7#

viscid shard
compact pewterBOT
# foggy wing 2/x+3=-1/x

Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.

foggy wing
dense dagger
#

You want to solve for x?

foggy wing
foggy wing
#

Teacher told us about proportion way but what if there's negative number😨

dense dagger
#

start by bringing all the x terms to numerators. So multiply both sides by x+3 to eliminate the x+3 in the denominator of the LHS. Repeat with x.

foggy wing
#

Ok i will figure it out

#

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old mica
#

Let $M$ be a smooth manifold with or without boundary and $p$ be a point
of $M$. Let $\mathscr{I}_p$ denote the subspace of $C^\infty(M)$ consisting of smooth functions that vanish at $p$, and let $\mathscr{I}_p^2$ be the subspace of $\mathscr{I}_p$ spanned by functions of the form $fg$ for some $f, g \in \mathscr{I}_p$.
\begin{enumerate}
\item Show that $f \in \mathscr{I}_p^2$ if and only if in any smooth local coordinates, its first-order Taylor polynomial at $p$ is zero. (Because of this, a function $\mathscr{I}_p^2$ is said to \textbf{vanish to second order}.)
\item Define a map $\Phi: \mathscr{I}_p \to T_pM$ by setting $\Phi(f) = df_p$. Show that the restriction of $\Phi$ to $\mathscr{I}_p^2$ is zero, and that $\Phi$ descends to a vector space isomorphism from $\mathscr{I}_p/\mathscr{I}_p^2$ to $T_p^*M$.
\end{enumerate}

boreal girderBOT
#

higher!

old mica
#

I'm trying to do part 1, the <- direction

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i.e. first order Taylor vanishes -> f is in I_p^2

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here's what I have so far

#

Conversely, suppose that the first order Taylor polynomial of $f$ at $p$ vanishes in any smooth chart $(U, \varphi)$ containing $p$, and use Taylor's theorem to write
\begin{align*}
\hspace{-20px} f(x) & = \underbrace{f(p) + \sum_{i = 1}^{n} \pdv{f}{x^i} \left(p\right) (x^i - p^i)}{= \ 0} + \underbrace{\sum{i, j = 1}^{n} (x^i - p^i)(x^j - p^j) \int_{0}^{1} (1 - t) \pdv[2]{f}{x^i}{x^j} \left(p + t(x - p)\right)}{R_1(x)} \ \
& = \sum
{i = 1}^{n} (x^i - p^i) \sum_{j = 1}^{n} \left(x^j - p^j\right) \int_{0}^{1} (1 - t) \pdv[2]{f}{x^i}{x^j} \left(p + t(x - p)\right)
\end{align*}
for any $x \in \varphi(U)$. Now set [f_i(x) = (x^i - p^i), \quad g_i(x) = \sum_{j = 1}^{n} \left(x^j - p^j\right) \int_{0}^{1} (1 - t) \pdv[2]{f}{x^i}{x^j} \left(p + t(x - p)\right).] Then $f(x) = \sum_{i = 1}^{n} f_i(x)g_i(x)$, and both $f_i$ and $g_i$ vanish at $x = p$.

boreal girderBOT
#

higher!

old mica
#

so now I'm stuck: I've obtained the result (f = sum of functions f_ig_i that vanish at p) within the chart U, but I don't know how to extend this to all of M

sullen merlin
#

Without thinking too hard ||partitions of unity go brrr?||

old mica
#

right?

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oh wait

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I was thinking of bump functions, but those would decay and it'd be doomed

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but partitions of unity are always 1 everywhere catthink

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okay lemme try this thumbsupanimegirl

sullen merlin
#

In general whenever you have a construction locally you want to extend to a global one, in partitions of unity you trust

old mica
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I dunno why I cast them out of my mind

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ig I just assumed they wouldn't work without thinking harder clopencry

sullen merlin
#

||Also as an aside: This result you're proving is actually how cotangent and tangent spaces are defined for more abstract spaces||

old mica
#

yeah ISM has a remark on that

sullen merlin
old mica
#

apparently people define the cotangent space first as I_p/I_p^2

#

and then set the tangent space to be the dual

#

this sounds kinda cursed to me since idk anything other than the very basic smooth setting, but I imagine it's useful when people leave this little bubble

sullen merlin
old mica
#

you say we can define the co/tangent space on more abstract spaces with this

#

wdym by that?

sullen merlin
#

meanwhile in the algebraic geometric setting one does have ideals

#

and here J_p and J_p^2 are two ideals

#

so taking their ring theoretic quotient is very natural

old mica
#

interesting catthink

#

I have much to learn, it seems holoapple

#

anyhow, thank you for the hint lance blobsatisfied

#

I shall close this now

#

.close

compact pewterBOT
#
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sullen merlin
compact pewterBOT
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short ferry
#

<@&268886789983436800>

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solemn matrix
#

I needed help with this question for $x \in \mathbb R$. I tried letting $a = \sqrt{x}$ and $b = \sqrt{x - 1}$, this results in $(a + 1)(a + b) = \frac{9}{2}$. This is neat but the fractions are annoying to deal with. What can I try?

boreal girderBOT
#

1 divided by 0 equals Infinity

open plaza
#

what other equation do you get

solemn matrix
#

a^2 + a + b + ab = 9/2
a^2 + ab + a + b = 9/2
a(a + b) + (a + b) = 9/2
(a + 1)(a + b) = 9/2

#

the most annoying thing to deal with is the 9/2

#

somehow, the calculator can't solve this equation too

open plaza
solemn matrix
boreal girderBOT
#

1 divided by 0 equals Infinity

open plaza
#

in other words a^2 - b^2 = 1

#

now multiply 1 to the right hand side (yes it is a legitimate hint)

solemn matrix
#

i see

solemn matrix
#

a = -b is one possible case

#
a^2 + a + b + ab = 9/2
a^2 + ab + a + b = 9/2(a^2) + 9/2(b^2)
(a + 1)(a + b) = 9/2(a - b)(a + b)

?

#

isn't a + b = 0 then a = -b?

boreal dawn
solemn matrix
#

thanks for reminding me of that

#

so $a + 1 = \frac92(a - b)$

boreal girderBOT
#

1 divided by 0 equals Infinity

solemn matrix
#

$a < b$ $\forall a, b \geq 0$

#

$\Leftrightarrow a - b < 0$ $\forall a, b \geq 0$

#

$\Leftrightarrow RHS = \frac92(a - b) < 0$ $\forall a, b \geq 0$

#

but $LHS = a + 1 \geq 1$ $\forall a, b \geq 0$

boreal girderBOT
#

1 divided by 0 equals Infinity

solemn matrix
#

so this is not possible

open plaza
#

√x <= √x-1 wa lao eh

solemn matrix
#

but you get my point

boreal girderBOT
#

1 divided by 0 equals Infinity

open plaza
#

you just made a big mistake there lmao

boreal girderBOT
#

1 divided by 0 equals Infinity

solemn matrix
#

thanks for reminding me of that lol

boreal girderBOT
#

1 divided by 0 equals Infinity

open plaza
solemn matrix
#

im going to think on this question

open plaza
#

is this for some olympiad stuff

solemn matrix
open plaza
#

chuyên rách

#

ko chơi

solemn matrix
open plaza
#

trường rách

solemn matrix
#
a = sqrt(x - 1)
b = sqrt(x + 1)
=> b^2 - a^2 = 2

(b^2 - a^2)(a + b) = 9a^3
(a + b)^2(b - a) = 9a^3
boreal dawn
solemn matrix
#

something like this

solemn matrix
open plaza
solemn matrix
#

√x > √x-1, not <=

open plaza
#

đòi học chuyên

#

tuah

solemn matrix
#

hell nah

#

.close

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#
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grizzled elk
compact pewterBOT
grizzled elk
#

so this might be bad, but i only know the first step of this

#

so take a point 0,0 , transforms to 0 0

#

then lets take the left most point -2,2

#

transforms to 1,3

#

then 2,2 transforms to-2,2

compact pewterBOT
#

@grizzled elk Has your question been resolved?

compact pewterBOT
#

@grizzled elk Has your question been resolved?

rotund sphinx
#

This means that you should figure out how T acts on $(1,0)$ and $(0,1)$

boreal girderBOT
#

Civil Service Pigeon

rotund sphinx
#

problem is that you're not given those

#

however, recall that because $T$ is linear, $T(\alpha \mathbf{u}+\beta \mathbf{v})=\alpha T(\mathbf{u})+\beta T(\mathbf{v})$

boreal girderBOT
#

Civil Service Pigeon

rotund sphinx
#

think about how you can use that combined with these pieces of info to find $T(e_1)$ and $T(e_2)$

boreal girderBOT
#

Civil Service Pigeon

compact pewterBOT
#
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#
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west pulsar
compact pewterBOT
west pulsar
#

Hey guys, I’m working on problem one right now

wide dune
#

what've you done so far?

west pulsar
#

Literally nothing

#

Would the first step be getting rid of the parentheses?

#

Idk my teacher didn’t tell us what do when there’s parentheses

#

We’re just finding asymptotes

wide dune
west pulsar
#

Just start with that?

#

Ok well
I have 24x^4 -5x^2-36

#

What now

#

<@&286206848099549185>

shadow abyss
west pulsar
#

1

#

I’m finding asymptotes

shadow abyss
#

tbh couldnt you just square root the entire thing

west pulsar
#

What

#

Why would you

shadow abyss
#

what is an asymptotes

shadow abyss
west pulsar
#

No

shadow abyss
#

what is an asymptote

wide dune
west pulsar
#

No but

#

Is that

#

Necessary?

wide dune
#

dude you gotta just try random shit sometimes and see what happens

#

you can't know it's necessary until you actually try to solve the problem

west pulsar
#

Yeah ig but like

#

Blech idk we never had to do that in class but at the same time it’s like

#

We never did it in class

wide dune
#

just distribute the denominator for now and see what happens

west pulsar
#

Ok what now

wide dune
#

now you have an x^4 term in the numerator and denominator

west pulsar
#

So

#

Multiply by 1/x^4?

#

.close

compact pewterBOT
#
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compact pewterBOT
#
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proper forum
#

I need help

compact pewterBOT
proper forum
#

I'm not sure how to solve this problem

#

It seems easy, but the word "rotate" is confusing me

proven wren
#

that's a convoluted way to ask for intersection of two line segments

proper forum
#

um..?

#

what is convoluted?

#

🙁

wide dune
# proper forum um..?

you have 2 line segments AB and A'B', the point where they intersect is the axis about which they rotate

proper forum
#

ohhh

#

Do they intersect?

proper forum
open plaza
wide dune
proper forum
#

what is full line whoop

#

actually the two lines don't intersect each other at all

open plaza
#

clearly the intersection isnt the center of rotation

proper forum
#

oh

#

if we prolong the line

#

I mean expand

proper forum
open plaza
#

there are 2 points that satisfy this

proper forum
#

wat are they>.?

open plaza
#
  1. The intersection of the perpendicular bisectors of AA' and BB'
  2. The intersection of the perpendicular bisectors of AB' and BA'
proper forum
#

ohh

#

then what is the right point?

open plaza
#

both points should be right

open plaza
proper forum
#

no

#

see the question

open plaza
#

I checked the coordinates of the correct points

#

and found both of them are included in the options

proper forum
#

wtf

open plaza
#

I don't know if the question specifically wants A -> A' and B -> B' after rotation

compact pewterBOT
#

@proper forum Has your question been resolved?

proper forum
#

I will just see the solution

#

gg

compact pewterBOT
#
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compact pewterBOT
#
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slate socket
#

I have a math test on 25th this month, can anybody guide me how to study and some tips as well please, I can let you know my syllabus

dusky nymph
#

do practice exams if you can find any

slate socket
dusky nymph
#

cover up the solution, do the problem on separate paper

wanton ferry
#

please write something specific

dusky nymph
#

try to do it in the same conditions (closed book, calculator or not, etc) as the real exam

#

and under the same time limits

slate socket
#

Oh

slate socket
wanton ferry
#

like the syllabus

wide dune
slate socket
wide dune
#

if you need study tips in general, this isn't really the place for it

slate socket
slate socket
slate socket
wanton ferry
#

yeah

#

and i still dont know how to help you review 20 subjects

slate socket
#

cool

#

maybe tell me about few

#

geometry part mainly

#

Similarity, Circles, Section Formula, Equation of a Straight Line

slate socket
wanton ferry
#

be specificccccccccccc

slate socket
#

these topics: Similarity, Circles, Section Formula, Equation of a Straight Line

wanton ferry
#

thats still too generalllllllllllllllllll

slate socket
#

wait imma let you know more

slate socket
#

obv not all

#

just few

wanton ferry
#

maybe just lemme help you on one topic and open a new channel for another topic

slate socket
#

Sure

slate socket
wanton ferry
#

can you hang in there i gotta help another channel xd

slate socket
#

just one topic as you asked

wanton ferry
#

v quick

slate socket
#

Yes sure

#

no problem, I'm glad that you are helping me

wanton ferry
#

bad news: you will have to memorise nearly everything here

#

but theres still intuition to help

#

yeah this is so dense

#

exactly which parts do you not understand

slate socket
slate socket
#

how should I or would you study this chapter (for the first time)?

#

or maybe even suggest me a youtube video on how to study math, if you have or think that can help

wanton ferry
#

so if you see angles whose vertexes lie on the circle, theres a high chance you should use one of the angle properties. if you see a quadrilaterall whose angles satisfy those conditions you should draw a circle that passes through all points. if you see two chords passing through a single point you should use the power of the point theorems. if you see a single tangent, you can probably draw a line from the center to the point of intersection. if you see two tangents passing through a point, you should know that they are equal

#

now, this may seem that im restating the theorems but the key takaway is that if you see any of these things theres a very high chance that the theorems will work

#

also sorry, this is still very general for us to help

slate socket
#

Thank you so much

wanton ferry
#

and the very important thing is to do problems

#

and also

#

reverse thinking

#

like, when you see the thing you prove, think what should you prove in order to prove that. you can also rewrite a strange answer using similarity identities to make it less weird

#

algebraically

compact pewterBOT
#

@slate socket Has your question been resolved?

compact pewterBOT
#
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compact pewterBOT
#
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sand magnet
#

two second order ODEs (dx^2+a(x)dx+c(x))psi=0 y (dx^2+d(x))psi=0 can have the exact same set of solutions?

noble sorrel
gaunt lynx
sand magnet
#

I want to prove it

#

okay, I send the picture, one moment

#

I mean, I want the answer and a proof of why yes/no

gaunt lynx
sand magnet
#

these* equations

#

ah psi depends on x

hushed magnet
#

if a(x)=0, c(x)=d(x), sure

sand magnet
#

well yes

#

but not doing that

#

I cannot do a=0

hushed magnet
#

well psi could satisfy (a d/dx+c)psi=d(x)*psi

sand magnet
#

yep

hushed magnet
#

which is just another ode which could have a solution

sand magnet
#

I've arrived to a compatibility condition, yeah

#

but this does just mean the intersection is not the vacuum

gaunt lynx
# sand magnet

For them to have exact same set of solutions then the fundamental solution of one equation must also be the solution for other, so ig you gotta so psi1 and psi2 and find solution

sand magnet
#

of the solutions

gaunt lynx
sand magnet
#

what do you mean?

#

My theory forbids a(x) from being zero

#

physical theory*

sand magnet
#

Yes, that's the proof I would like to have

gaunt lynx
#

You’ll have to assume psi1 and psi2 for fundamental sets and then find solution for both the conditions

sand magnet
#

can you prove it by first solving a solution and then the other?

gaunt lynx
#

Try it the way you think, and if doesn’t work, try it the way i suggested

compact pewterBOT
#

@sand magnet Has your question been resolved?

compact pewterBOT
#

@sand magnet Has your question been resolved?

sand magnet
#

yep but I'm not able to prove it

rotund sphinx
# sand magnet

No. From the second equation, we have that
$$\dv[2]{\psi}{x}=-d(x)\psi$$
Substitute this into the first equation:
$$-d(x)\psi+a(x) \dv{\psi}{x}+c(x) \psi=0$$
$$a(x) \dv{\psi}{x}+(c(x)-d(x)) \psi=0$$
$\psi$ can be described as a linear combination of two linearly independent basis solutions $\psi_1$ and $\psi_2$. Thus, $\psi_1$ and $\psi_2$ are solutions to the same first-order ODE, which is impossible as they must be linearly independent.

boreal girderBOT
#

Civil Service Pigeon

compact pewterBOT
#

@sand magnet Has your question been resolved?

#
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sand magnet
#

thankss

compact pewterBOT
#
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fallen frost
#

Calculus -- In the following type of limit, does dt have the same value as h?

mild sky
#

dt is not a number

#

its notation that is part of the integral

fallen frost
#

hmm, my current impression is that this is basically 'f(t) * h', which amounts to the area of the rectangle sliver being integrated.

kind viper
#

it is just a notational device

#

which NOTIONALLY stands for the width of a tiny increment on the t-axis and is sometimes illustrated as such

#

however it must not be taken literally

fallen frost
#

.close

compact pewterBOT
#
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honest merlin
compact pewterBOT
honest merlin
#

im so confused whats happening in part b please help

#

what's the formula for curvature?

kind crane
#

In mathematics, curvature is any of several strongly related concepts in geometry that intuitively measure the amount by which a curve deviates from being a straight line or by which a surface deviates from being a plane. If a curve or surface is contained in a larger space, curvature can be defined extrinsically relative to the ambient space. C...

honest merlin
#

okay I guesssssss I'll read into it

#

.close

compact pewterBOT
#
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#
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paper tendon
#

hi, i have an exercise:

How many triangles can be created if each side can be one of the following lengths: 4, 5, 6, 7, 8, 9 (+ no two triangles are congruent)

My logic is

The lengths can be used multiple times and the order doesnt matter (467 is same as 476), so we use combinations with repetition + there are 2 combinations from which triangles cant be created (4,4,9 and 4,5,9)

My result: (8 choose 3) - 2

Is my logic correct ?

weak cobalt
#

What about 4,4,8

paper tendon
#

Ye forgot that one

#

So 3 combinations

weak cobalt
#

Not sure how (8 choose 3) answers that

fluid stag
#

Is 4,4,8 considered a triangle?

paper tendon
weak cobalt
#

pandathink yeah I think you're correct

remote current
#

I don't think the choose function is correct if you allow repeat lengths

#

maybe I am wrong though

paper tendon
weak cobalt
#

Right, right, 5+3 choose 3

remote current
#

ah mb, I think you are right

paper tendon
#

ye results say its correct thx all

#

.close

compact pewterBOT
#
Channel closed

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paper tendon
#

.reopen

compact pewterBOT
paper tendon
#

if someone has more intuitive way to think about this, let me know, i just used the equation but im not really sure why it works, maybe i just need to go over the logic of the combinations but not sure

weak cobalt
#

It's about putting things in boxes

#

You have 6 lengths, those are your boxes

paper tendon
#

ye i know the boxes and divisors logic

weak cobalt
#

You must select 3, with repetitions, so you're putting 3 things in those 6 boxes

paper tendon
#

ill just go over it again

weak cobalt
#

That's 5 dividers + 3 things, so 8 things total, and you need to choose 3

paper tendon
#

ye this makes sense, maybe im just struggling with transforming it into the combination number

weak cobalt
#

You can also consider cases: 6 equilateral triangles, 6*5 isosceles triangles (the 6 is for the length of two sides, the 5 for the third length), and 6*5*4 / 3! other triangles (/3! to remove duplicates)

paper tendon
#

ye makes sense

#

why cant it be just 6 * 5 * 4

#

oh

#

nvm i see

weak cobalt
#

xxx||||| would be choosing the first 3, x||x|||x would be choosing the 1st, 4th, and 8th

#

Once you can visualize examples, it should be clear how to get the formula

paper tendon
#

ok, thx a lot

#

i will post couple more exercises to verify my logic if u dont mind, if someone else wants to correct me im down, if not i will just close this channel and look at the results

#
a library has 5 shelves and each can hold 20 books, how many ways can we place 20 books

my logic

there is total 100 places at the beggining to place a book so my result would be: V(20, 100) = 100*99*98*...*81
strong crest
paper tendon
#

ye seemed too good to be true, the results say 24!/4!

strong crest
#

Right, well it’s a slightly ambiguous question but

paper tendon
#

there was also a hint that i forgot to mention: "you can think of shelves next to each other where each two shelves are divided by same item"

strong crest
#

Sure, I don’t think (I might be wrong) they want you to think of each shelf as something with 20 slots

paper tendon
#

so its permutations with repetitions where each book is different and we have to divide by all possible permutations of divisors

strong crest
#

I think they want you to just think of the shelf as something you can put up to 20 books on, so the real problem is how many ways can we distribute the 20 books among 5 shelbes

paper tendon
#

is my guess

strong crest
#

In other words, any 5 numbers that add up to 20

#

But it also depends on whether the books are identical or not

paper tendon
#

probably not

strong crest
#

Mmm well if they are distinct then the answer is kind of easy to calculate but it’s not 24!/4!

paper tendon
#

we can probably think about it like BBBBBBBBBBBBBBBBBBBBDDDD where B is a book and D a divisor

strong crest
#

Yes so the books are all alike

#

And you’re right yes

paper tendon
strong crest
#

If they were distinct the answer would be

#

5^20

paper tendon
#

how come

#

variations make more sense to me

strong crest
#

There are 20 books, each one you have 5 shelves to choose from

paper tendon
#

without repetition

strong crest
#

So itll be 5x5x5…..20 times

#

But that’s only if they’re distinct

paper tendon
#

ok i guess it makes sense

#

thx

strong crest
paper tendon
#

ye, Nel mentioned it 20 messages above

strong crest
#

You might notice it’s a stars and bars problem

paper tendon
#

yep makes sense

#

another exercise:

a selfcheckout cofee shop has 4 types of coffee, each has 50 grams. how many combinations of 250g of coffee can we buy
a) if there is enough coffee of all types

my logic

stars and bars again, 3 divisors (bars) and 5 coffees (stars), so result 8!/(3!*5!)
#
b) if 2 types of coffee have 10 packs of coffee each and rest of the coffee types only have 4 packs

my logic

we take result from a) and decrement 2 for the two coffee combos where we cant create 5 of the same type
#

both are actually correct, these were easier for me so i just checked results

#

thx all

#

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rotund ether
#

Determine all positive integers n such that there exists a positive integer m with the property that n is divisible by m and n² + m² is divisible by m²n + 1.

hello can someone help me with this ?

compact pewterBOT
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rotund ether
#

wait sorry ill ask again later thank uu

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trail yew
#

What is the definition of a definition in geometry as in definition of angle bisector

grizzled geyser
trail yew
#

What don’t you understand about your question

#

My*

#

I just realized I mistyped

#

It should make sense now

kind crane
#

what is the definition of definition?

grizzled geyser
#

In mathematics, a definition is used to give a precise meaning to a new term, by describing a condition which unambiguously qualifies what the mathematical term is and is not. Definitions and axioms form the basis on which all of modern mathematics is to be constructed
According to Wikipedia

trail yew
#

Oh ok

#

I have a few more questions if you don’t mind be asking

#

Hello are u still here?

kind crane
trail yew
#

Ok

kind crane
#

for this one: there's no widely accepted convention. you just figure it out from context

#

not really enough context to answer this one:

#

and the rest are just done with practice. do more actual problems

trail yew
#

There’s the problem where I had the question

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soft sundial
#

Proof that angular displacement AOT = -OAT

Hey! I’m working on an engineering project with angular displacements - it’s basic trig with the caveat that I need angles to preserve their sign as they’re displacements and i’m using a polar coordinate system.

Can anyone perhaps give me a few slight hints as to how I could elegantly prove the relationship I demonstrate in this picture? I think this is a great opportunity for me to practice my proofs so the vaguer you can start off the more awesome 😁 thanks!

soft sundial
#

I could use the coordinates of A and T but I feel like I should be able to do it just from this 🤔

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@soft sundial Has your question been resolved?

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@soft sundial Has your question been resolved?

soft sundial
#

Basically if we “pivot” at O and sweep from A to T the “angle” is negative because that’s a clockwise sweep which is a negative angle vector in a polar space :)

#

But if we pivot at A and sweep from O to T the angle vector is counterclockwise, which is positive in polar coordinates

#

Unfortunately the classic engineer’s vibes-based proof aint gonna cut it 😭 i’d like to prove this mathematically

soft sundial
#

.solved

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stiff flume
compact pewterBOT
stiff flume
#

not sure how to simplify the derivative in terms of dx and dy

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tall pecan
#

hi

#

you there

#

first you have to differentiate the y = wx to make a differential equation

#

so that you can substitute parts of the differential equation given

#

then you will get a short equation, which has to be integrated

#

then with the point A(e^2, 0) you will get the value of the constant

#

then finally put the value of constant

#

@stiff flume

stiff flume
#

hm

tall pecan
#

don't have to integrate the function, proceed with differentiating y = wx

#

you seeing?

#

hey ping me when u r free

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rocky berry
#

How would I go about finding if something is differentiable on an open interval

rocky berry
#

Do I derive the function then set it equal to 0 to solve for x then put the numbers of the interval back into the original function to see if it is equal to what I got for x

stark marsh
rocky berry
#

So like how does this show that

compact pewterBOT
#

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rocky berry
#

Is it where they solve for x on the derivative and find it equal to -3

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leaden leaf
#

Whats the best way to cram for PSAT math?

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flint cliff
#

Would the top view or plan view of the screw be a circle with diameter 23mm

hard isle
#

.

#

need help?

steep crypt
#

Me

hard isle
#

say

#

what q

steep crypt
#

What q?

upper bane
compact pewterBOT
# steep crypt Me

Someone else is already using this help channel. If you need help with a question, please open your own help channel/thread (see #❓how-to-get-help for instructions).

steep crypt
#

What di you mean

hard isle
#

oh

#

i meant what question

#

this is occupied

#

🥀

upper bane
#

if you want to ask a question, please use an available channel, like #help-29

#

don't use a channel with a | and a person's name in the title

hard isle
#

ping me

#

@steep crypt

steep crypt
#

Yo

strange ermine
#

!noping

compact pewterBOT
#

Please do not ping individual helpers unprompted.

upper bane
hard isle
upper bane
#

and you didn't notice OP has already opened a channel?

hard isle
#

um no

upper bane
#

plus, there are already people helping OP

#

now, let's stop flooding this channel

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#

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flint cliff
#

.close

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tall lantern
#

Can someone help me?

#

<@&286206848099549185>

kind crane
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noble copper
#

does PA.PB mean PA * PB

compact pewterBOT
noble copper
#

?

thorny urchin
#

yes

noble copper
#

oh

fossil finch
#

ig yes

noble copper
#

ok

strange ermine
compact pewterBOT
# noble copper ok

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noble copper
#

!done

compact pewterBOT
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If you are done with this channel, please mark your problem as solved by typing .close

noble copper
#

.close

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versed wraith
#

.close

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sacred wave
#

Hello I need help

compact pewterBOT
sacred wave
#

I’m trying to calculate the effective rent on a loan but i keeps getting 0%

#

Its in Danish so it hard to understand

#

<@&286206848099549185>

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glossy sentinel
#

Question: If A is an n × n matrix with entries in R satisfying (A^T)A = 2In, show that A is
always invertible.

Do I multiply each side by 1/2 to isolate the In matrix so 1/2(A^T)A = In. After this I am lost.

open girder
glossy sentinel
#

The determinant of 2In? or what? I'm not given the A matrix.

open girder
#

(A^T)A = 2I_n ==> det((A^T)A) = det(2I_n)

open girder
glossy sentinel
#

ok, ty. I got it.

#

.close

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raw dawn
#

This look correct

compact pewterBOT
dusty harbor
#

why you got it in blue light

#

but yeah looks good i think, id have to solve it to really know

raw dawn
raw dawn
#

preferably using the same methods I did

#

I had a teacher solve it but she got a slightly dif answer that idk if it’s equivalent

dusty harbor
#

it looks like you messed up somewhere

#

gimme a sec to finish my q rq

raw dawn
dusty harbor
#

wrong

#

place

#

sorry

raw dawn
#

lol

raw dawn
#

What a throwback

dusty harbor
#

can you help me w it then

raw dawn
#

Lemme try

#

it’s been a min

dusty harbor
raw dawn
#

Also didn’t think of the u sub

#

lol

dusty harbor
raw dawn
#

Bro don’t mess with trig sub

#

It’s my favorite

dusty harbor
#

yeah

#

thats crazy

#

ive not done trig sub since i had to 😭

#

im struggling over here

raw dawn
#

@dusty harbor

dusty harbor
#

yeah

raw dawn
#

I split it up like CRAZY

#

If u want my work

#

lol

#

30π

dusty harbor
#

hm

#

yeah show me

#

please

raw dawn
#

I did the u sub for cos2theta but js didn’t show it, it equals 0 anyway

raw dawn
dusty harbor
#

but thank you abhsbshah

raw dawn
#

U subtracted

#

Not multiplied

dusty harbor
#

also sorry to say, i cannot help you opencry

#

atl w trig sub

#

forgot that long ago

raw dawn
#

lol

#

I try to stay updated

dusty harbor
raw dawn
#

I haven’t been w calc 3 lol

dusty harbor
#

from 2pi to pi

raw dawn
#

I lowk js split it up a shit ton

dusty harbor
raw dawn
dusty harbor
#

if you take it anyway

#

oh

raw dawn
#

I mean keeping up with it

dusty harbor
#

ohhhh

#

type

#

for why

raw dawn
#

If you gave me a spherical triple integral idk if I’d be able to solve it lol

dusty harbor
#

you in uni or no?

raw dawn
#

Nah

#

Senior yr hs

dusty harbor
#

damn

#

another child prodigy

#

sick of this world

raw dawn
#

Wbu*

raw dawn
dusty harbor
#

2nd year of uni opencry

raw dawn
#

my friend who’s the same age is a soph in college rn

#

😭

dusty harbor
#

bro some 14 year old was helping me w this not too long ago 😭

#

i cant handle this no more

raw dawn
#

It’s also def a lil easier to get ahead in hs

dusty harbor
#

biochemistry

#

last year of math 🙏

raw dawn
#

I went from alg 2 (the end) to calc 3 and Lin alg (the beginning) in a year

raw dawn
dusty harbor
#

yeah but honestly its not that bad

#

im just brain dead

#

and i think also linalg

#

but thats cake

raw dawn
#

It was in my calc 3 over the summer which was a 6 week course

dusty harbor
#

yeah kudos

#

6 week courses are brutal

#

you're dual enrolled?

raw dawn
#

Nah

#

Not offered at my school

dusty harbor
#

interesting

raw dawn
#

I’m ahead of evb else