#help-13

1 messages · Page 251 of 1

maiden venture
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To find a point or do I add t or something?

burnt vapor
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You want to find the line l

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So you need a point and a vector

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Q is in l so you already have a point

maiden venture
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Yes

burnt vapor
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And l is perpendicular to π, so n is the vector

maiden venture
#

Yes okay

burnt vapor
#

So you can find l

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Now, if l is a line that contains Q and is orthogonal to π, what is the orthogonal projection of Q onto π?

maiden venture
#

N - Q?

burnt vapor
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Why?

maiden venture
#

Well I don’t know I am just guessing

burnt vapor
#

Do you know what the orthogonal projection is?

maiden venture
#

No

burnt vapor
#

Then you should study and understand it before trying to do a problem about it

#

You should at least know a formula to find it or something

#

Otherwise you can't do anything

maiden venture
#

.close

cedar kilnBOT
#
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cedar kilnBOT
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crimson sedge
cedar kilnBOT
crimson sedge
sturdy rose
#

lets start somewhere

dusty hazel
#

do you know when f(x) is negative? Or when f(x) is positive?

gilded mesa
#

Put the values

scenic brook
#

Should we expand

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:?

crimson sedge
gilded mesa
#

No expansion

scenic brook
#

Ok

dusty hazel
crimson sedge
#

Oh uhh

scenic brook
#

Oh, you can make a graph

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🙂

coral jewel
scenic brook
#

To find signs

crimson sedge
#

This is a dsat question, I can use desmos

scenic brook
#

Damn...

coral jewel
#

the x^2 coefficient is >0, so the graph should be u-shaped

gilded mesa
coral jewel
#

and since at x=1 and x=7 f(x) is positive, the minimum of the graph should be between 1-7

#

that should be your first clue

scenic brook
#

👍

crimson sedge
#

We need a + b

scenic brook
#

Of course

coral jewel
#

a rough sketch of the graph

scenic brook
#

It says possible values

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Not exact

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Idk

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So you just use graph

gilded mesa
#

Graph is difficult

scenic brook
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Method of intervals or whatever

coral jewel
#

heres another hint: the equation is under the form (x-a)(x-b), therefore a and b are the 2 roots of the equation

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essentially, you are finding the possible sum of the two roots

crimson sedge
#

Ok can someone tell me steap by step what to do? I'll really confused

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Ok I gotta go, I'll just ask my teacher tomorrow

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Sorry

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Thank you everyone

#

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cedar kilnBOT
#
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gilded mesa
#

I figured out
4<a<7
1<b<4
@crimson sedge

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You just have to put value of x inside function

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We need just one value a+b not exact value

#

We can assume a and b by these interval

cedar kilnBOT
#
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dull plover
#

hi

cedar kilnBOT
dull plover
#

sorry im a freshman taking calc 1 and im a bit unfamiliar with the general terms of integrals

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i know that the integral of any variable ie x^n is x^n+1 / (n+1)

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but the symbols here got me confused as im new to them

chrome flax
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$\int dx = \int 1 dx$

wraith daggerBOT
#

Xotiic

chrome flax
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1 is just x^0

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so add 1 to the power and divide by that and you’d have x

dull plover
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makes sense but what exactly is dx here

supple flume
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derivative of x

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basically

dull plover
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im familiar with the derivative notations

supple flume
#

to tell you what you are integrating

dull plover
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but im completely oblivious to how they work in this context

chrome flax
#

Yh it tells you what you’re integrating with respect to

dull plover
#

so if u were saying

supple flume
# dull plover

if it said dk you would be integrating k in this integral

crimson sedge
supple flume
crimson sedge
#

dx is a differential, the derivative of x is 1

dull plover
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so if u were to turn the first note into words

#

what would it read as

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the integral of any constant is x+c?

supple flume
supple flume
supple flume
dull plover
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because its k * x^0

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yeah

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what about dx alone

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isnt it x^1

supple flume
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or the integral of 1 * x^0 dx

dull plover
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yes what does that exactly mean

dull plover
supple flume
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if you see a constant term just remember theres and x^0 in there

dull plover
#

well what about

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x dx

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what does this mean

supple flume
#

well whats the power rule?

dull plover
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is it just talking about the variable x raised to any power

dull plover
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yeah i get it now

supple flume
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k could be anything

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well it doesnt work for x^-1

dull plover
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im familiar with the technicalities but i was just confused with the official formula bc its been a while since i last took integral calc 😭

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anyways ty

supple flume
dull plover
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like

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oh i see where this is going

supple flume
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(u cant divide by 0 so u cant use the power rule for this)

dull plover
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yeah this is all we took

supple flume
dull plover
#

figured 😭

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i have an exam this saturday with the basics of integration and the fundemental theory of calculus

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wish me luck

supple flume
#

good luck lol

cedar kilnBOT
#

@dull plover Has your question been resolved?

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slender mango
#

Hey

cedar kilnBOT
slender mango
#

I need to transalte this

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for what $a$ is vector u and v paralell if $\vec{u}=(-2,a+1,-4)$ and $v=(a,-1,2)$.

wraith daggerBOT
#

Totalani

slender mango
#

what I did was $(-2,a+1,-4)=\lambda(a,-1,2)$

wraith daggerBOT
#

Totalani

slender mango
#

Which gave me $$\begin{cases}
a\lambda=-2 \
-\lambda=a+1 \
2\lambda=-4
\end{cases}$$

wraith daggerBOT
#

Totalani

slender mango
#

Kinda stuck here, not sure if I did it correcly up to now?

#

nvm think I got it

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yup I got it

#

.closer

#

.close

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slender acorn
#

Find the square of:
3a-2b-5c

cedar kilnBOT
slender acorn
#

Shall I start like this?

dire geode
slender acorn
#

oh sorry

#

actually 2b-5c should have become 2b+5c

#

.close

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wet fossil
#

R = {(1,3),(1,5),(2,3),(2,5),(3,5),(4,5)}
Is R^-1 = {(y,x) | (x,y) belongs to R}?

slate lintel
#

yeah

deep hull
wet fossil
#

Alright, so
R⁻¹ = {(3,1),(5,1),(3,2),(5,2),(5,3),(5,4)}
R○R⁻¹ = {(1,1),(1,2),(1,3),(1,4),(2,1),(2,2),(2,3),(2,4),(3,1),(3,2),(3,3),(4,4)??? but this is not even in options

deep hull
#

oh it ended

slate lintel
#

what does ○ mean?

wet fossil
#

Composition

novel isle
#

From a point P on the bisector of angle AÔB, draw a line that forms four congruent angles with and intersects the sides of angle AOB, or their extensions, at points C and D. Prove that:
a. OC = OD;
b. for any point Q on OP, QC = QD

wet fossil
#

Does the O (in ROR⁻¹) mean something else here?

novel isle
#

I’m sorry where I have to go?

slate lintel
slate lintel
#

remember in R○R⁻¹, R⁻¹ gets applied first

wet fossil
#

ohh yeah right my bad

#

thanks!!

slate lintel
#

here's this to help you lol

wet fossil
#

thanks

#

got it

#

.close

cedar kilnBOT
#
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woeful mason
#

Hello, I appologies as im French Canadian the terms I use might be different than what ive wrote as ive basically just tried to translate it.

I'm having a real hard time to understand and do "Formal System"

The first image are the rules that I have that allows me to transform things and so on

The second image is an example, but when Im trying to follow it I get blocked at the 2nd step.

woeful mason
cedar kilnBOT
woeful mason
#

So basically each line represents one step the result, and the rule used one what

(1) x v z premise
Means that is step one of my formal system, the result is x v z, and its just a premise available in my theorem

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while
(2) ~x => v (1), r(9)

means its step two, the result is ~x => v after than I applied the rule 9 on the first result

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When I look in the tables of rules above, I dont understand how the rule 9 is being applied and where the negation comes from

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as x v z doesnt contain any negation

upper abyss
#

Rule 9 says:
A → B
Is exactly the same as
~A V B

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Oh wait nvm they're combining two rules into rule 9

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Rule 9 also says:
A → B
Is exactly the same as
~B → ~A

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That "second rule 9" is what they're using in step 5.

woeful mason
#

I understand that, but what I dont understand is how my x v z can be applied in the rule nine, there is no negation in it

upper abyss
#

Okay we are talking about rule 2, not rule 5. My bad, I got mixed up

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Then we refer back to the "first rule 9" lol

#

Rule 9 says:
A → B
Is exactly the same as
~A V B

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Now, you're saying there's no negation. Note the negation needs not be there

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It's the relationship between the symbols that actually matters

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If I were to, say, substitute ~A in for A, then this is also rule 9:
~A → B
Is exactly the same as
A V B

woeful mason
#

so A v B can be applied the rule 9 ? you then switch it to ~A => B because you just "note" that there is supposed to have a negation at the start meaning that you have to inverse it at the end?

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or yeah as you say you just subsitute it, but at the end you have to put it back?

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(A => B) <-> (~B => ~A) <-> (~A v B)
is the same as
(~A => B) <-> (~B => A) <-> (A v B)

#

if I understand

woeful mason
#

ok thank you!

#

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#
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dull plover
#

how is this expression valid

cedar kilnBOT
dull plover
cedar kilnBOT
dusty hazel
#

Is this photomath?

dull plover
#

sin^2(x)+ cos^2(x) = 1

#

shouldnt it be 1 - cos^2(x)

dull plover
dusty hazel
#

They want to say sin^2(x) or (sin(x))^2

dusty hazel
dull plover
dusty hazel
#

But cos(2x) = cos^2(x) - sin^2(x)

dusty hazel
dull plover
#

ohhh

#

we used that formula instead

dusty hazel
#

Pretty much used both of them, but yeah.

dull plover
#

wait

#

can u do a step by step

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of the substitution

dusty hazel
#

cos(2x) = cos^2(x) - sin^2(x) = 1-2sin^2(x)

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Solve for sin^2(x) in terms of cos(2x)

dull plover
#

2sin^2(x) = 1 - cos(2x)

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sin^2(x) = 1/2 - 1/2cos(2x)

#

yea makes sense now

#

ty /!

#

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livid stratus
#

An infinite Geometric series that is going down is given. a1,a2,a3,,,an. its Quotient is Q. and its numbers are positive. using the numbers from the given sequence we set a new.

livid stratus
#

prove if the new sequence is a Geometric series or not.

#

<@&286206848099549185>

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latent wolf
#

find a set of parametric equations for the line of intersection of the planes 3x+2y-z=7 and x-4y+2z=0

latent wolf
#

Hello 🙂

lavish quest
#

3x+2y-z-7 = x-4y+2z ?

#

wait

latent wolf
#

Is that how I need to rewrite my equation?

lavish quest
#

i guess

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What does z represent?

latent wolf
#

I'm supposed to write a parametric equation for the line of intersection

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I have the answer, I'm just not sure how they got there

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x = 2
y = 1 + t
z = 1 + 2t

lavish quest
#

So the question is what exactly did he want?

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if x = 2 3x = 6 btw

latent wolf
#

Right

lavish quest
#

then 3x+2y-z = 7

latent wolf
#

The question is how did he come up with the equation for the line

lavish quest
#

2y-z-1 = 0?

latent wolf
#

I don't understand how he came up with 0i+1j+2k

lavish quest
#

You can produce an equation that depends on y

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or z whatever

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what did he do

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i dont see

latent wolf
#

I don't know all I have is the answer

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one sec

lavish quest
#

Does it want intersection point

latent wolf
lament root
#

The first one can use the dot product definiton with cosine?

latent wolf
#

Ya I managed to get the angle easy enough

lavish quest
#

wait

#

let me look at it

lament root
#

Well lets start by taking z=0

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Solve the first two equations for x and y

lavish quest
#

lets look at here

lament root
#

Then, we use that vector to take a cross product with the normals of both planes

latent wolf
#

Lemme see if I can snip my work into here

lavish quest
#

ok

latent wolf
young bane
#

hello is someone willing to help me with analytics geomtry ?

lament root
#

That is crucial in finding the normal to the intersection

latent wolf
#

When I did the cross products I ended up wiht 0i-7j-14k

young bane
#

hi

lavish quest
#

@latent wolf You will handle it my friend

#

@young bane You can write to another channel, or dm

young bane
#

okay

lavish quest
#

@young bane But next time you want help, write to another empty channel

young bane
#

oh okay sorry

lament root
latent wolf
#

Is it possible for me to share my screen in here?

lament root
latent wolf
#

I'll snip

#

So if I know that x = 2 and I set z=0

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or am i missing something

lament root
#

So you have a point. Now you need the normal

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The normal is found by cross product of the normals of eq1 and eq2

latent wolf
#

So for the cross product of the normals of eq1 and eq2

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I end up with 0i-7j-14k

#

<@&286206848099549185>

#

<@&286206848099549185>

#

Hello?

#

<@&286206848099549185>

cedar kilnBOT
#

@latent wolf Has your question been resolved?

latent wolf
#

<@&286206848099549185>

#

<@&286206848099549185>

#

<@&286206848099549185>

#

<@&286206848099549185>

#

<@&286206848099549185>

frigid hemlock
#

buddy relax

latent wolf
#

just tryna get some help fam

cedar kilnBOT
#

@latent wolf Has your question been resolved?

latent wolf
#

.close\

#

.close

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untold holly
#

My guy is in middle of the exam

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vital beacon
cedar kilnBOT
vital beacon
#

Does anyone know how to get the horizontal asymptote of this equation?

slate lintel
#

limit as x goes to infinity or negative infinity

vital beacon
#

oh

#

how does that work

#

OHHH I get it

#

thanks

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keen raven
cedar kilnBOT
#

Please don't occupy multiple help channels.

keen raven
#

im not

#

oh wait

#

ok i closed my old one

#

Why do I multiply by conjugate

#

Does it matter if I multiply by 5-sqrt(7)

#

Wont that still cancel out

#

why is it +

crimson sedge
#

,,<cancel>\def\CancelColor{\tc r}\f4{\cancel{5-\s7}} \c b{\cd \f{\cancel{5-\s7}}{5-\s7}} =\f4{5-\s7}

void sand
#

difference of squares

wraith daggerBOT
crimson sedge
#

so you are not saying much by what you are doing

keen raven
#

Oh

#

Oops

#

ye...

lavish quest
#

i think it is (-10-2√7)/12

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multiply by 5+√7

#

top and bottom

cedar kilnBOT
#

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last trench
cedar kilnBOT
last trench
#

14B please

cedar kilnBOT
last trench
#

how do i find the centre and radius of the circle of intersection

#

thats the equations

#

plsss

cedar kilnBOT
#

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upper abyss
#

9 = (10 - 1)

#

Mind you, that leads heavily into number theory

#

But binomial-esc

#

You'll see it every time now lol

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celest marsh
#

Is there any software I can use to double check my tuple relational calculus queries?

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@celest marsh Has your question been resolved?

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autumn tusk
cedar kilnBOT
autumn tusk
#

This is cc differential equations. He's explaining ERF.
I don't understand the first line. Shouldn't be (D+a)(D+b) ?

#

a and b are roots

upper laurel
#

on the second line, p' presumably means dp/dD or if you want ∂p/∂D

autumn tusk
#

He's differentiating the first line. A step which I also don't understand

#

My first problem is the first line

silver oxide
#

yeah no the video is right

#

(d-b) means that b is a root

#

same concept for a

gilded mesa
#

So a and b are root of D^2-(a+b)D+ab

#

=

#

0

#

What you mean by root

#

It says root case

autumn tusk
#

The roots of the characteristic polinomial.

gilded mesa
#

Oh

silver oxide
#

if (d-b)(d-a) = 0, meaning they are roots then d-b=0 and therefore d=b, same concept for a

autumn tusk
#

I mean the second term coul also be positive right?

silver oxide
#

why would it be positive?

gilded mesa
autumn tusk
gilded mesa
#

Function of x and constant

autumn tusk
#

I mean the second term of the diff

upper laurel
#

the minus sign isnt to tell you that the number is positive or negative

gilded mesa
#

Not have function of y there

upper laurel
#

its to have you subtract instead of add if the root is plugged in

#

(x - 3)(x - 2) has roots 3 and 2 which can be seen by plugging them in
(x + 3)(x + 2) has roots -3 and -2 which can be seen by plugging them in

gilded mesa
silver oxide
#

P(D) has roots when P(D)=0 therefore (d-b)(d-a) = 0, meaning that d-b is a root and d-a is a root therefore d=b and d=a are roots

autumn tusk
gilded mesa
#

Not respect to x

upper laurel
#

try differentiating (x - 3)(x - 2)

#

youll see you get (x - 2) + (x - 3)

autumn tusk
#

Ooooo

#

Ok gotcha

upper laurel
#

bruh

autumn tusk
upper laurel
#

it no longer means anything if you do that but p(D) = (D + a)(D + b) sure is a polynomial that has the letters D, a, and b in it

#

its derivative dp/dD is (D + b) + (D + a)

autumn tusk
#

Why means anything?

upper laurel
#

is that a bad thing?

autumn tusk
#

I don't get it...

#

I'm lost

silver oxide
#

well what even is the goal?

upper laurel
#

if it takes a single misread sentence to dislodge your understanding then you have some big questions to answer

#

what did you get before

autumn tusk
#

I was following a video and he jumped on this proof.

#

I'll rewatch the video after work.

upper laurel
#

it helps you no longer get lost by restarting back to "what was I stuck on again"

autumn tusk
#

Ok thanks

#

.close

cedar kilnBOT
#
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elder elm
#

could someone help me with this problem'

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novel ginkgo
#

hello

cedar kilnBOT
novel ginkgo
#

how can i solve this

#

2:3 is the ratio of foods delivered (fries to chips). if they had delivered 4 more fries, the rario would be 3:4, how mang fires n chips they delivered in total?

quiet plover
#

Then the ratio would be 2:3

#

And then solve

novel ginkgo
#

how can i solve it is there a way to find out the total number other than substituting the choices

#

thank u for your response!

quiet plover
#

Ok wait

#

Say there are f number of fries

#

And c number of chips

#

so f/c = 2/3 right?

novel ginkgo
#

yes

quiet plover
#

Now cross multiply

#

3f=2c

novel ginkgo
#

okok

quiet plover
#

After dividing by 2

#

c = 3f/2

novel ginkgo
#

okioki

quiet plover
#

Now we just need to find c

#

So how can we represent 4 more fries

#

f + 4

novel ginkgo
#

ohhh

#

c = 3(f+4)/2

#

?

quiet plover
#

The ratio is not 2:3

novel ginkgo
#

ohh i see whre i got wrong

quiet plover
#

Look at the questin

novel ginkgo
#

is 3:4 after adding fries

#

i see now

quiet plover
#

(f+4)/c = 3/4

quiet plover
novel ginkgo
#

ohhh nice

quiet plover
#

You'll get 3c = 4(f+4)

#

3c = 4f + 16

#

Now you can substitute the value of c

#

And solve for f

novel ginkgo
#

THTS coooool

#

thank u so much

#

!!!

quiet plover
#

But I think the neater answer would start with the fries and chips being 2y and 3y

novel ginkgo
#

ohhh i see i see

#

thank u blurple !

quiet plover
#

welcome

#

You can close the chat using .close now

cedar kilnBOT
#

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near quiver
#

The sum for the real numbers a and b for which the limit (photo) is equal to:

near quiver
#

!status

cedar kilnBOT
#
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
near quiver
orchid pilot
near quiver
#

The limit of the square root would be +infinity I assume.

#

I never had this a and b unknowns to limits, I am quite new to limits, actually. Just about 2 weeks in.

orchid pilot
near quiver
#

Minus infinity I assume?

#

a can be any real number though...

orchid pilot
#

we have to search for a value a thats gives us a finite limit

#

try to do that

#

try to get x^2 out of the sqrt

#

so get something like |x|sqrt(.....) - ax

near quiver
#

Mhm..I will certainly try and think of a way, I will come once I'd find anything or give up.

orchid pilot
#

yes try and lmk

near quiver
#

You mean a forced factoring?

#

Of the x^2, such that we would have the x^2 out as x(something)?

orchid pilot
#

and then you can get the x^2 out of the sqrt

near quiver
#

Now. I assume I can't factor x and its absolute value.

orchid pilot
#

no so first

#

we have to simplify this

#

this can be done by getting rid of the sqrt

#

do you have an idea how?

near quiver
#

Well, the limit of 1/x for either plus or minus infinity will always be 0?

orchid pilot
#

yes

near quiver
#

So, the radical will be 1

orchid pilot
#

yes so what will be left is |x| + ax = b

#

right?

near quiver
#

Precisely.

#

I make two scenarios?

orchid pilot
#

no

#

you know that x will be negative

near quiver
#

Ah, true.

orchid pilot
#

so only the case where x is negative

#

so what do get?

near quiver
#

x - ax = b?

orchid pilot
#

no you made a mistake

#

ax will not change

#

it is |x| that has to be rewritten for negative x

#

because of the absolute value

#

so the term ax will remain untouched

near quiver
#

Hm, because we don't touch ax at all and let it remain positive?

#

I thought by x being negative, it would be a no brainer to write "-ax"

#

The absolute value makes sense, obviously.

orchid pilot
#

so want to rewrite the absolute value in terms of x and not |x| so we can a common factor with ax

#

how to do that in case that x is negative

near quiver
#

x(1-a)=b?

orchid pilot
#

not really\

near quiver
#

-x(1+a)=b ?

orchid pilot
#

no

#

so what is |x| when x is negative

near quiver
#

still x

#

Positive*

#

My bad.

orchid pilot
#

yeah so we have to turn the sign

#

so how can we do that?

near quiver
#

Into negative, by multiplying with (-1)?

orchid pilot
#

yes so we find that...

#

|x| = -x when x<0

#

which is true in our case because the limit is negative

#

so what do we get now?

near quiver
#

ax - x = b?

orchid pilot
#

yes

#

we can rewrite as

#

(a-1)x=b

#

now think of a case where this limit can be true

near quiver
#

I realised, didn't I make a mistake? -b?

#

Or I am multiplying only the LHS?

orchid pilot
#

we do you think that

#

yes only lhs

near quiver
#

Ohh because of the specific x requirements.

orchid pilot
#

because we want to get rid of abs of x

#

yes yes

near quiver
#

Great, now...

orchid pilot
#

in what case is this limit never infinity

near quiver
#

When a-1 and b are 0?

orchid pilot
#

yes

#

so we now solve for a

#

and take the sum

near quiver
#

Which a+b is just 1

#

Bingo. We did it.

#

Thanks for the help man, appreciate it lots.

#

Have a great day/evening!

#

.close

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#
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dense herald
#

.close

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royal finch
#

If you already know how to calculate the maximum likelihood from earlier parts, what part of this alternate version is challenging

#

I'm not going to read that, but if you can calculate this you should recognize that the computation for an MLE is broken up into a few steps. Namely writing down the likelihood function, then optimizing it.

#

The optimization step is just calculus, you find a critical point and you exploit the log convexity of the normal to guarantee that the critical point is the optimal value

#

Now, you have a case where mu must lie in [0,1]

#

So either the critical point is in [0,1] or it isn't. And you should know from Calculus where the optima lies if there is no critical point in your region of interest

#

The point is that by drawing a picture of a quadratic on the interval [0,1]

#

You have your answer

cedar kilnBOT
#

@wicked willow Has your question been resolved?

cedar kilnBOT
#

@wicked willow Has your question been resolved?

cedar kilnBOT
#

@wicked willow Has your question been resolved?

bold wyvern
#

can you reformulate the question neatly from the beginning ?

cedar kilnBOT
#

@wicked willow Has your question been resolved?

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sturdy rose
#

Find the number of ways to distribute 21 identical oranges among 3 children such that all of them get atleast 2

sturdy rose
#

i know i can use ramanujans partions

#

and i can use multinomial

#

apart from these two, is there any other way to solve these questions?

cedar kilnBOT
#

@sturdy rose Has your question been resolved?

tropic slate
#

just wondering

#

is the asnwer 136

sturdy rose
#

but using partions, it does come out to be 136

tropic slate
#

im pretty sure i used partitions

cedar kilnBOT
#

@sturdy rose Has your question been resolved?

sturdy rose
#

.close

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bold mauve
#

If you draw 3 cards from a standard deck of 52 what is the probability your first card is a space given the second and third card are a spade?

sturdy rose
#

do you know what revised probability is?

bold mauve
#

No

#

I have setup $E_i$ to be the event that the $i$-th card was a space: $$P(E_1|E_2E_3)$$

wraith daggerBOT
sturdy rose
#

hm

bold mauve
#

Im doing it like this

#

I expand $$P(E_1|E_2E_3) = \frac{P\left(E_{1}E_{2}E_{3}\right)}{P\left(E_{2}E_{3}\right)}$$

wraith daggerBOT
bold mauve
#

Using basic properties of conditional probability

#

but I don't understand why my answer is wrong

#

$$\frac{\frac{4}{52}\cdot\frac{3}{51}\cdot\frac{2}{50}}{\frac{4}{52}\cdot\frac{3}{51}\cdot\frac{2}{50}+\frac{48}{52}\cdot\frac{4}{51}\cdot\frac{3}{50}}$$

wraith daggerBOT
bold mauve
#

For P(E1 E2 E3) I thought we have 4 in 52 cards being a space, 3 in 51 on the second draw, and 2 in 50 on the third draw

#

then for P(E2 E3) that is the situation P(E1 complement E2 E3) + P(E1 E2 E3)

sturdy rose
bold mauve
#

They are not replaced

#

Is revised probability bayes theore

#

I know what that is

sturdy rose
#

well what youre doing is what i would do, so the name isnt important

bold mauve
#

these are the identities we are given

#

I used the top one

#

oh I computed it wrong because I didnt know what a deck of cards was I thought spade was a card denomination like king or queen

#

$$\frac{\frac{13}{52}\cdot\frac{12}{51}\cdot\frac{11}{50}}{\frac{13}{52}\cdot\frac{12}{51}\cdot\frac{11}{50}+\frac{39}{52}\cdot\frac{13}{51}\cdot\frac{12}{50}}\ $$

wraith daggerBOT
bold mauve
#

this comes out to the right answer

#

.close

cedar kilnBOT
#
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cedar solstice
cedar kilnBOT
alpine rune
#

,rotate

wraith daggerBOT
cedar solstice
#

Question 85

alpine rune
#

okay

#

what did you try so far?

cedar solstice
#

I choosed one seat for the child that come first

#

6c1

#

And

#

Then

#

For worst case

#

Another child have to choose another seat

#

So 5c1

#

+1 for the the possibility that the second child get the seat he needed

#

And other three got their respective seats

#

Divided by total cases

#

I am not able to find total cases

#

And idk if what I did is correct or not

alpine rune
#

hi

#

sorry im here

cedar solstice
#

Did i choosed the cases correct

alpine rune
#

hold up

cedar solstice
#

K

alpine rune
#

ooh aakash byju's

cedar solstice
#

Lol

alpine rune
#

jee? 😭

cedar solstice
#

Answer the question

#

Yup

alpine rune
#

yea doing that

alpine rune
#

well from what I could deduce, we know that the first student must select a seat out of any of the 3 seats that are not of the last 3 people. so the probability he does that hs 1/2 (3/6). the next student must also select a seat randomly that isn't of the last 3 people, so 2/5, and then 1/4. I'm giving it a second thought though because im not really sure if that would be the answer because I think im missing something

#

so like (3/6 * 2/5 * 1/4)*120 🤷‍♂️

cedar solstice
#

Might be the answer

#

I couldn't find the answer online anywhere to this question

alpine rune
#

ok

#

well check if this is right then, I think that should be it

cedar solstice
#

It seems right to me

#

Thanks for the help

alpine rune
#

alright

cedar solstice
#

Can you please check 84 also I got the answer 6

alpine rune
#

yeah that's right

cedar solstice
#

K

#

Thanks

#

Bye

alpine rune
#

no worries

#

ok

cedar solstice
#

.close

cedar kilnBOT
#
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cedar solstice
#

.reopen

cedar kilnBOT
#

cedar solstice
#

Wait I have one more question

alpine rune
#

shoot

cedar solstice
#

Question no 82

alpine rune
#

ok

#

hmm

#

you know that omega = 1/omega^2

cedar solstice
#

Yup

alpine rune
#

nevermind I don't think that's taking us anywhere

#

hmm

#

back

cedar solstice
#

Any progress??

alpine rune
#

well all I could think of is using brute force and expanding it

#

but im sure there's some other way out

cedar solstice
#

It would take years

alpine rune
#

yeah it would

#

is it 2

cedar solstice
#

Idk

autumn kindle
#

im getting 4

#

no wait

#

let me do it again

autumn kindle
#

i got it

#

what u can do is

#

u can create a polynomial equation

#

1/(a+x) + 1/(b+x) + 1/(c+x) + 1/(d+x) = 2/x

#

now roots of this are w, w^2

#

make it a 4 degree equation

#

and use sum of roots

#

product of roots

#

the answer is 2

alpine rune
#

or you could divide both sides in the first equation by omega, then compare the denominators or something (aw^2 + 1 = a + w^2) and I I'd like to think that'd get you somewhere

autumn kindle
#

u got the answer?

alpine rune
#

yeah

autumn kindle
#

kk

alpine rune
#

this would make it easier

autumn kindle
#

yeah

alpine rune
#

because that gives you a = b = c = d = 1

autumn kindle
#

ohh

#

i see

alpine rune
#

so its 1/2 * 4 = 2

autumn kindle
#

right

#

faster

#

lol

#

no wait what

#

how did u get

#

a = b = c = d = 1

alpine rune
#

aw^2 + 1 = a + w^2

#

solve this, same for bw^2 + 1 = b + w^2

autumn kindle
#

oh im dumb

#

nvm

#

the thing is

#

here this method is allowed

#

cuz there is symmetry

alpine rune
#

yeah

#

that's why I used this

autumn kindle
#

yeah

alpine rune
#

its not the best method in other cases but in other cases im sure there's some other way

autumn kindle
#

yeahhh

cedar solstice
#

Thanks guys

alpine rune
#

ok

cedar solstice
#

.close

cedar kilnBOT
#
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autumn kindle
#

k

cedar kilnBOT
#
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eternal pollen
#

What is derivatives of functions?

cedar kilnBOT
sturdy rose
#

"functions"?

#

a derivative is the differentiation of a function wrt to x (mostly)

sturdy rose
eternal pollen
#

ahh okay

#

also

#

since the average rate of change is written as Δy/Δx, why is instantaneous rate of change written as dy/dx?

#

is it just to make them visually different?

sturdy rose
#

but theres a big difference

#

like literally

#

one of them indicates a very minute change

#

and one indicates a considerably big chance

eternal pollen
eternal pollen
#

.close

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#
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random grove
#

Trying to better understand the proof behind this proposition in my lecture notes.

I think the idea behind the whole proof is that if you can find a bounded subsequence, then by Bolzano-Weirestrass theorem, there exists a convergent subsequence of the original bounded subsequence. If there isn't a bounded subsequence , meaning no convergent subsequence, then by the definition of a limitpoint, then the limitpoint set is empty. i've probably worded it really poorly but I hope it makes sense. pictures include the proposition with its proof and then the definition of a limitpoint set

random grove
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I just want some clarification is my reasoning is correct or not in order to better my understanding

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ah the definition didnt send. here it is:

cedar kilnBOT
#

@random grove Has your question been resolved?

cedar kilnBOT
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spare mountain
#

Is anyone here familiar with Radix Conversion in Hash values?

spare mountain
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Here's one of the given:
Key Value: 24680
Radix Conversion (Base 9 to Base 10): 56

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But when I converted 24680 from base 9 to base 10, I got 16596 so the Radix Conversion value should have been 96.

cedar kilnBOT
#

@spare mountain Has your question been resolved?

cedar kilnBOT
#

@spare mountain Has your question been resolved?

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warm spear
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Idk how to start... Do I rationalize the denominator? Do I open tan into sin and cos?

livid hound
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i'd recommend starting with a sub like u=sqrt(x)

crimson sedge
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then it will become easier to work your head around it.

mighty shuttle
wraith daggerBOT
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Why am. I here

warm spear
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I don't know what sub is...

sturdy rose
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uh

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you really should

warm spear
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Okay I think I get what sub means

#

So far correct?

sage forge
warm spear
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?

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But that one is from dx=du?

sage forge
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Yes, but you need to rewrite it in terms of u as well

warm spear
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Really?

sage forge
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Yes

warm spear
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Huh that's new

sage forge
warm spear
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So now I should claim integral and open (u) and my question is solved?

#

It's correct,Awesome! Thanks!

#

Now I know how to use "u substitution"

#

Can this also be used in limits?

#

Or it's for integrals only

sage forge
warm spear
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Limits and integrals HAVE A CONNECTION?!?!

warm spear
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What.,...

#

How and where do I even begin?

sage forge
# warm spear

The sin(4x) is bothering me a bit. Can you use a trig identity to rewrite it?

#

Maybe in terms of something depending on 2x

sage forge
warm spear
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For the cos²(3x) yes but for the sin i don't think so

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Can I claim a 2 in any way from the sin's degree (4x)? To make it a 2x or that's mathatically impossible

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My phone battery is dying, I'll be back after a few minutes

sage forge
warm spear
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Making it (2sin(2x)cos(2x))?

sage forge
sage forge
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Because now you only have sin(2x) and cos(2x). That is advantageous for a substitution

warm spear
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I wonder can i also pull out a (minus) from the denominator and separate the minus with the (1) to make it (1-cos^2(2x)) to tun it into -sin^2(2x)? Or I am now making things up?

slow kiln
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do u need the steps?

warm spear
slow kiln
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1+cos2(2x) actually

warm spear
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All of it?

#

Oh I see

slow kiln
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if u take it, differentiate it with respect to x, you'll get the numerator which is 2sin(2x)cos(2x) with an extra -2

slow kiln
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so its easy from there

warm spear
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Got it, thanks!

slow kiln
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no problem 😄

warm spear
slow kiln
warm spear
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I had doubts about it

slow kiln
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ignore the messy numbers its a bit rushed my bad

slow kiln
sage forge
#

Please do not give out full solutions. The point of a help channel is to guide the helpees and not do the exercises for them.

warm spear
slow kiln
warm spear
sage forge
warm spear
slow kiln
warm spear
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Is multiplication

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Yes yes got it, my brain was in an other world

slow kiln
warm spear
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Also sorry for not using mathematical terms I didn’t learn it in English to recognize them

slow kiln
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nah even i dont know enough and appropriate mathematical terms, im literally gambling with the words im using here

warm spear
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Lol

sage forge
warm spear
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Ok that’s all for now, I will go back to study and might…well…will come back later because I’m sure I will have more questions

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Thank you all again!

warm spear
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Yep

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I will just open another when I come back

slow kiln
slow kiln
sage forge
slow kiln
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i plan to do my higher studies there

warm spear
slow kiln
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hopefully

slow kiln
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im assuming you're from india too

warm spear
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Neighbors xd

sage forge
slow kiln
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all depends on that one uni

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besides i would need to learn german

sage forge
sage forge
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.close

cedar kilnBOT
#
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slow kiln
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oh uh

cedar kilnBOT
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subtle hinge
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noticee how every alternate term leaves remainder 0

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and the other ones 1

cedar kilnBOT
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ocean basalt
#

Question:
Jessica stretches her arms out 0.60 m from the center of her body while holding a 2.0 kg mass in each hand. She then spins around on an ice rink at 1.1 m/s.
What is the combined angular momentum of the masses?
If she pulls her arms in to 0.15 m, what is her new linear speed?

My work so far:
r = 0.6 m
m = 2 kg
v = 1.1 m/s

The combined angular momentum of the masses is given as
L = mvr + mvr
L = 2mvr
Inserting the values:
L = 2(2)(1.1)(0.6)
L = 2.64 kg m^2/s

I'm stuck on how to calculate the new linear speed. If anybody could help out, it would be appreciated.

subtle hinge
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bro mathematics server for a reason

ocean basalt
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huh

#

could u help out

subtle hinge
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i ssuck at phy

near quiver
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He means that this is a physics problem in a maths server

subtle hinge
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altho i shall try

subtle hinge
near quiver
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No worries, well you are lucky someone already tries this

near quiver
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MagnusOP said he'd try?

crimson sedge
ocean basalt
subtle hinge
near quiver
#

Ohhh

subtle hinge
dusky peak
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uhm

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She then spins around on an ice rink at 1.1 m/s.

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how do you spin with a velocity?

#

or do they mean this as the velocity of the balls

ocean basalt
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masses

dusky peak
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kk

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ok so

#

quick tip: dont calculate stuff

#

in this case, you correctly got the value for L

#

you also got a formula

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L=2mvr

#

if she pulls her arms in, angular momentum will be conserved

subtle hinge
dusky peak
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if we call that new momentum L', then we get:
L=L'

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the new angular momentum will have the same formula:
L'=2m' v' r'
note however, that m didnt change, so m'=m

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so now we can set L equal to L' and rearrange to v'

ocean basalt
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ok

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so how would this look with the values inserted in?

dusky peak
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we dont wanna look at values right now
putting in values before the end just makes it messy

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we have L=2mvr, L'=2mv'r'
with L=L', we get
2mvr=2mv'r' => vr=v'r'

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that way we also avoid rounding errors

ocean basalt
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alright

#

.solved

cedar kilnBOT
#
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ocean basalt
#

Ciara is swinging a 0.015 kg ball tied to a string around her head in a flat, horizontal circle. The radius of the circle is 0.70 m. It takes the ball 0.60 seconds to complete one full circle. Calculate the tension in the string and its direction that provides the centripetal force acting on the ball to keep it in the circular path. (3 points)

0.0077 N, toward the center of the circle

1.2 N, toward the center of the circle

0.0077 N, along the line tangent to the circle

1.2 N, along the line tangent to the circle

dusky peak
#

.reopen

cedar kilnBOT
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dusky peak
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.

#

.

#

open

cedar kilnBOT
dusky peak
#

astro said:
Ciara is swinging a 0.015 kg ball tied to a string around her head in a flat, horizontal circle. The radius of the circle is 0.70 m. It takes the ball 0.60 seconds to complete one full circle. Calculate the tension in the string and its direction that provides the centripetal force acting on the ball to keep it in the circular path. (3 points)

0.0077 N, toward the center of the circle

1.2 N, toward the center of the circle

0.0077 N, along the line tangent to the circle

1.2 N, along the line tangent to the circle

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ok so

#

i get something completely different than the 4 choices

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but the direction should be easy

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do you see what it should be?

#

@ocean basalt

ocean basalt
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i think so

dusky peak
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centripetal forces are perpendicular to the movement

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so in this case they point towards the center of the circle

#

but is the force 1.2 N or 0.0077 N?

#

given m, r, T
we can first derive the angular velocity w=2 pi / T

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and then we can use the formula for the centripetal force
F=m v^2/r = m w^2 r

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the thing is that when i do the math here, i dont get 1.2 or 0.0077

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oh well, they might have rounded

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yeah thats probably it

#

did you try to calculate it @ocean basalt ?

cedar kilnBOT
#

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cedar kilnBOT
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green mulch
#

Need to find the perimeter of the triangle ABC , the ratio of the sides are not common ratios and the ar. Of the inner triangle is 60cm²

spiral fog
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So like the ration that some dot split AB is 1 : 3?

green mulch
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Yeah

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This is what I did

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Can't figure anything else

spiral fog
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Yeah thats good

green mulch
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Anything u can think of doing next?

spiral fog
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Fun problem i will think about it

green mulch
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Yeah thanks I have been thinking about it for 2 days

spiral fog
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Any progress?

green mulch
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Nothing

jaunty pumice
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U can use coordinate

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Geo

green mulch
#

Came up with something but my teacher proved it wrong

spiral fog
green mulch
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Can u show me how?

spiral fog
#

But i mean everything can be solved analytically so...

jaunty pumice
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Like let point R be origin