#help-49

1 messages · Page 70 of 1

twilit field
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I think the bot will be down for a while

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I have a class now, so I'll continue from where I left in an hour

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.close

midnight plankBOT
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Channel closed

Closed by @twilit field

Use .reopen if this was a mistake.

twilit field
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thanks a lot for the help!

frank wolf
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np

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wait

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is this what people are supposed to do…?

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I thought there was like

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!noclopen

midnight plankBOT
#

Please don't repeatedly close and claim a new channel with the exact same question. This erases all previous progress made towards your problem and is confusing for helpers, making it more difficult to help you. Please be patient, even if your channel has not received much attention.

humble torrent
#

yeah maybe posting it in the help forum would of been wiser

midnight plankBOT
#
Available help channel!

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Remember:
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After 15 minutes, feel free to ping <@&286206848099549185>.
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last slate
midnight plankBOT
last slate
dreamy lichen
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Almost, except for 1 point

last slate
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huh

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2 ?

dreamy lichen
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there will be the empty circle

last slate
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desmos doesn't show that ?

last slate
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or not ?

safe oriole
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press on the point on the graph with x=2

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on desmos

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it will show an empty circle

dreamy lichen
last slate
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it says undefined

hard umbra
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x = 2 is not even in the domain

dreamy lichen
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it will be 0/0 when you plug in x = 2

last slate
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nvm it shows an open circle

dreamy lichen
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I actually drew it lol

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because that's how it's commonly drawn by hand

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desmos doesnt plot those 1 point discontinuities

last slate
last slate
dreamy lichen
hard umbra
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its just a weird question to ask when 2 isnt even in the domain of the function

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would you say that (x - 2)/(x^2 - 5x + 6) is discontinuous at x = sully?

last slate
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no

safe oriole
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this new function will be continuous at x=2 but the current y(x) isnt

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because there is no y(2)

last slate
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OH

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so

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i can't say

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this and y = 1/(x-3) are the same

dreamy lichen
last slate
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Okay

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i get it

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thanks everyone

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.close

midnight plankBOT
#
Channel closed

Closed by @gleaming geode

Use .reopen if this was a mistake.

midnight plankBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

twilit field
#

prove that $x-\frac{x^3}{6} \leq sin(x)$

midnight plankBOT
grand pondBOT
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ƒ(Why am. I here)=I don't Know

twilit field
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I've reached until here

frank wolf
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Ok so you have to prove this

twilit field
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$\sin(t) \leq t$ and $- \sin(t) \leq t$, we can deduce $2 \sin^2(t) - 2 t^2 \leq 0$

grand pondBOT
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ƒ(Why am. I here)=I don't Know

frank wolf
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Because?

twilit field
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No, I just wanted the bot to TeX what you just said

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I find it hard to read TeX

frank wolf
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Mhm

twilit field
grand pondBOT
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ƒ(Why am. I here)=I don't Know

frank wolf
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How?

twilit field
frank wolf
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Why are you allowed to do that?

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It’s not true in general that if x <= y then x^2 <= y^2

zealous schooner
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Hello there

zealous schooner
frank wolf
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Right

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That’s different from squaring both sides though

wintry galleon
zealous schooner
wintry galleon
frank wolf
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To be clear im not disagreeing that they can deduce sin^2(x) <= x^2 from the info they have

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I’m just not convinced they’ve done it yet

twilit field
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hmm, I don't follow

twilit field
dreamy lichen
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-2 < -1 but it's not true that (-2)^2 < (-1)^2

twilit field
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true

frank wolf
grand pondBOT
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Pseudonium

frank wolf
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And unfortunately “squaring both sides” doesn’t work

twilit field
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$x>sin(x)$ is always true

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
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now x is always positive

frank wolf
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When $x > 0$

grand pondBOT
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Pseudonium

frank wolf
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It’s not true for 0, or for negative x

twilit field
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so $x^2>sin^2(x)$ is always true too

wintry galleon
frank wolf
grand pondBOT
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ƒ(Why am. I here)=I don't Know

midnight plankBOT
twilit field
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for x>geq 0

frank wolf
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Why?

twilit field
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wait

frank wolf
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Unfortunately that’s not a proof..

twilit field
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I'll try justifying it

frank wolf
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Ok

twilit field
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so $x>sin(x)$ in Quadrant 1

grand pondBOT
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ƒ(Why am. I here)=I don't Know

twilit field
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with both being positive

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so $x^2>sin^2(x)$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

wintry galleon
frank wolf
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What’s quadrant 1?

twilit field
frank wolf
twilit field
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then from [π/2,π] x>sin(x)

frank wolf
zealous schooner
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$x^2>\sin^2 x\iff x^2-\sin^2 x>0\iff (x+\sin x)(x-\sin x)>0$

grand pondBOT
#

kheerii

dreamy lichen
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or at least opposite implication, what you had before wouldnt help

twilit field
frank wolf
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I don’t follow

zealous schooner
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Nvm

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Why are you proving x>sinx

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That’s given to you isn’t it?

twilit field
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in the interval [0,π/2] $x^2>sin^2(x)$

grand pondBOT
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ƒ(Why am. I here)=I don't Know

frank wolf
zealous schooner
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Yeah okay

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I think you’re going about it in too much of a roundabout way

twilit field
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now in the interval $[π/2, infty)$ x>1, so x^2>sin^2(x) as sin^2(x) is bound between 0 and 1

grand pondBOT
#

ƒ(Why am. I here)=I don't Know
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

zealous schooner
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There isn’t a need to split it into quadrants

frank wolf
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Oh

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Wait

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Waiiit

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Ah I see what you’re doing

zealous schooner
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Not necessary though

frank wolf
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Oh yeah that actually works I think

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Neat

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It’s not the proof I had in mind

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But it works

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Cool!

dreamy lichen
frank wolf
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I’m convinced for x >= pi/2 now

twilit field
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if a>b, and and b are both positive, a^2>b^2

frank wolf
frank wolf
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Ok cool

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Now im convinced that you’ve proven $x^2 \geq \sin^2 x$

grand pondBOT
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Pseudonium

dreamy lichen
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was it done for negative x already?

zealous schooner
frank wolf
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Oh well we were only worrying about x >= 0

zealous schooner
frank wolf
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But you can use evenness to deduce for negative x

dreamy lichen
frank wolf
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I don’t think it’s worth worrying about

dreamy lichen
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i just wanted it to be mentioned

frank wolf
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Sure!

twilit field
zealous schooner
dreamy lichen
grand pondBOT
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ƒ(Why am. I here)=I don't Know

dreamy lichen
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oh wait its something else

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nvm

twilit field
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thanks a lot everyone!

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.close

midnight plankBOT
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Channel closed

Closed by @twilit field

Use .reopen if this was a mistake.

frank wolf
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uh wait did we finish lol

twilit field
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yeah

frank wolf
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I don’t think we did

twilit field
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.reopen

frank wolf
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We haven’t gotten back to the original Q

midnight plankBOT
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twilit field
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ok

humble torrent
twilit field
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ok, so what do I have to prove now?

frank wolf
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back to the original Q?

twilit field
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I have proven it though, right?

frank wolf
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no?

dreamy lichen
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you have proven x^2 >= sin^2(x)

twilit field
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ok, so (x-x^3/6)-sin(x) <0

frank wolf
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where did you get that from

twilit field
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I differentiated the function

frank wolf
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huh

twilit field
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used some trig identities

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so 1-x^2/2-cos(x)

frank wolf
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i am not following what you’re doing..

dreamy lichen
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are you assuming that if f'(x) < g'(x), then f(x) < g(x)?

dreamy lichen
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i dont follow either then

frank wolf
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you seem to be doing something akin to

humble torrent
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are you integrating?

twilit field
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no

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I differentiated the function

frank wolf
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we want to prove A. We show $A \implies B$. We show B is true. Hence A is true

grand pondBOT
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Pseudonium

frank wolf
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This doesn’t work as a proof

twilit field
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I don't follow, why can't I prove that the function is decreasing

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I know it starts at 0

dreamy lichen
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which function though?

twilit field
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x-x^3/6-sin(x)

humble torrent
twilit field
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I'm trying to prove x-x^3/6-sin(x) <0 \froall x geq 0

dreamy lichen
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wait no

frank wolf
dreamy lichen
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oh it does

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nvm

dreamy lichen
twilit field
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well, I aim to show it's decreasing

twilit field
dreamy lichen
twilit field
#

the inequality effectively becomes $x-x^3/6-sin(x) \leq 0$

grand pondBOT
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ƒ(Why am. I here)=I don't Know

dreamy lichen
frank wolf
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$x - \frac{x^3}{6} \leq \sin x \iff x - \frac{x^3}{6} - \sin x \leq 0$

grand pondBOT
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Pseudonium

frank wolf
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This is how id phrase it

twilit field
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ah, ok

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thanks

frank wolf
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You see

frank wolf
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To me, this reads as

dreamy lichen
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or if you wanna use words, say "it suffices to prove that [Insert your inequation]"

twilit field
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I see

frank wolf
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$x - \frac{x^3}{6} \leq \sin x \implies x - \frac{x^3}{6} - \sin x \leq 0$

grand pondBOT
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Pseudonium

frank wolf
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To be clear, this statement is true

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But if you don’t use $\iff$, you can’t reverse the logic

grand pondBOT
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Pseudonium

frank wolf
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To get back to the original thing you want to prove

twilit field
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ah, okay

frank wolf
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When i see “A, so B”

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I read it as $A \implies B$

grand pondBOT
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Pseudonium

frank wolf
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Starting from A, one can deduce B

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Which is fine, except it won’t directly help you prove A

twilit field
#

so I have to write $A \iff B$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

frank wolf
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Yes (as long as that’s actually true)

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Cause what that communicates is that you can reverse your logic

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After all a proof is supposed to at least be a convincing argument

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So other people are going to read it

twilit field
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yeah, true

frank wolf
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And so it’s useful to make sure you’re communicating well

twilit field
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okay

twilit field
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or is the proof missing anything else

frank wolf
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You seem pretty eager to claim that your proof is done..

twilit field
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yeah, sorry

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I'm just trying to cover a lot of ground before uni starts

wind oxide
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is this done?

frank wolf
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don’t think so, no

twilit field
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no

frank wolf
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So, what’s the next step after $x - \frac{x^3}{6} - \sin x \leq 0$?

grand pondBOT
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Pseudonium

wind oxide
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cant u just

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taylor series this

twilit field
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I differentiiate it to get $1- \frac{x^2}{2} -cos(x)$

grand pondBOT
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ƒ(Why am. I here)=I don't Know

twilit field
wind oxide
#

Isnt that covered in like

dreamy lichen
wind oxide
#

HS

twilit field
frank wolf
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Wait it is?

twilit field
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I'm doing lang now

frank wolf
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I don’t remember Taylor series from HS..

twilit field
#

but no proofs

frank wolf
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Huh..

twilit field
#

just formula

frank wolf
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Right

wind oxide
twilit field
frank wolf
twilit field
wintry galleon
grand pondBOT
#

ƒ(Why am. I here)=I don't Know

midnight plankBOT
frank wolf
twilit field
#

1-cos(x) -x^2/2 is this

wind oxide
#

but

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your choice

twilit field
frank wolf
grand pondBOT
#

Pseudonium

twilit field
#

okay

frank wolf
#

And then?

wind oxide
twilit field
#

so x/2=t

frank wolf
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I would write “Let t = x/2”

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Since you’re defining a new variable

twilit field
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okay

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so I then have $2sin^2(t)-2t^2<0$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

frank wolf
#

I would recommend you write this as $2 \sin^2(x/2) - 2x^2 /4 \leq 0 \iff 2 \sin^2(t) - 2 t^2 \leq 0$

grand pondBOT
#

Pseudonium

quiet hinge
frank wolf
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Just to make clear how you’ll reverse your logic

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It’s just, whenever I see the words “so then” I assume you mean $\implies$ and not $\iff$

grand pondBOT
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Pseudonium

twilit field
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I mean $\iff$

frank wolf
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I’m sure you do! It’s just good to be explicit about it

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

frank wolf
#

In general, when I read proofs and see “so then”, it gets used as $\implies$

grand pondBOT
#

Pseudonium

twilit field
#

got it

twilit field
frank wolf
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What do you mean by “solve”? Do you mean you prove it?

twilit field
#

yes

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wait

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no

frank wolf
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Hm, then what do you mean

twilit field
#

I show that sin(t)<t

frank wolf
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Oh sure

twilit field
#

and that -sin(t)<t

frank wolf
#

We’ve already proved that $\sin^2(t) \leq t^2$ for $t \geq 0$

grand pondBOT
#

Pseudonium

twilit field
#

tes

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yes

frank wolf
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So I think it’s ok for you to use that fact now

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I won’t make you repeat that proof

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So what’s next?

twilit field
#

from that we know the function is decreasing

frank wolf
#

Which function?

twilit field
#

the OG function

frank wolf
#

Which is…?

twilit field
frank wolf
#

Where’s the function in that?

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I’m looking for something that I can plug a number into, and get back a number

twilit field
#

at 0, the function is 0

frank wolf
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Which function

twilit field
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the OG function

frank wolf
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You haven’t actually told me what function it is

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Or maybe - here’s another way to think about it

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What is the value of the OG function at 3?

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If it’s a function, I should be able to plug something into it

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Otherwise, I’m not convinced you have a function

twilit field
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3-27/6-sin(3)

frank wolf
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Aha!

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How’d you get that?

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What did you plug 3 into?

twilit field
#

I defined x-x^3/6-sin(x) to be f(x)

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and tried to show $f(x) \leq 0$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

frank wolf
#

Right, so you should write that explicitly

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So say

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“Let $f(x) = x - x^3/6 - \sin x$”

grand pondBOT
#

Pseudonium

twilit field
#

right

frank wolf
#

And you’re saying that this function is decreasing?

twilit field
#

yes, I have the mention that too I suppose?

frank wolf
#

Mhm

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So, why is it decreasing?

twilit field
#

it's derivative is always negative

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or equal to 0

frank wolf
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Indeed!

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So now I agree with you that the function is decreasing

frank wolf
twilit field
#

the function is 0 at 0

frank wolf
#

Indeed, so $f(0) = 0$

grand pondBOT
#

Pseudonium

twilit field
#

so if it's decreasing it can only be less than 0

frank wolf
#

Well…

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-x is decreasing too

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But it takes the value 1 at x = -1

wintry galleon
#

(when someone is doing the same thing though I wrote it clearly before)

frank wolf
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So you need to be a little more careful

frank wolf
wintry galleon
#

if you see that message

frank wolf
#

You did not guide them through it

wintry galleon
#

I clearly wrote which point we find

frank wolf
#

Guiding means, like, actually talking to them, and letting them come up with the solution themselves

wintry galleon
#

and we proved that it is increasing

frank wolf
#

Rather than merely providing an explanation

frank wolf
twilit field
frank wolf
#

Right

twilit field
#

so it can only become less than 0 ow

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*now

frank wolf
#

What do you mean by “it can only become less than 0”

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-x is also 0 at 0

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But it is not always <= 0

twilit field
#

the function is decreasing, ,so to the right of 0, it must be less than 0 from the defn of decreasing functions

frank wolf
#

Yes!

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So what you mean is that for $x \geq 0$, $f(x) \leq f(0) = 0$

grand pondBOT
#

Pseudonium

twilit field
#

I really've got to lean to include detail ded

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yeah

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makes sense

frank wolf
#

Mhm

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I’m sure I must seem pedantic and I’m sorry for that

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But it’s important to know how to get down to all the detail

twilit field
#

yeah

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I get that

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so what detail is the proof missing now

frank wolf
#

I think you’re probably done actually

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So long as you string everything together in a coherent way

twilit field
#

I'll do that, thanks!

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thanks a lot for all the help!

#

.close

midnight plankBOT
#
Channel closed

Closed by @twilit field

Use .reopen if this was a mistake.

stone blaze
midnight plankBOT
#
Available help channel!

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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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stable mirage
#

how do i find a 2nd line

midnight plankBOT
slender walrus
#

howd you get the first line

stable mirage
#

derivative is 2x+1

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slope of line that goes through (2,-3) would be 5

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y=5x+b

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-3=10+b

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b=-13

slender walrus
#

methodology is already incorect

stable mirage
#

oof

slender walrus
#

you shouldn't be plugging the point into that

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as that point isn't actually on the parabola

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derivative gives you slopes at points on the curve

stable mirage
#

what should i do

slender walrus
#

consider a point of tangency P(p, p^2 + p)

#

then set
slope between (2,-3) and P = derivative at P

stable mirage
#

ok

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and from there?

slender walrus
#

solve for p

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you should get two cases

#

you'll get a point / equation for each case

stable mirage
#

so

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do i set $\frac{p^2+p+3}{p-2} = 2p+1$?

grand pondBOT
#

MWB117

stable mirage
#

i got p = 5 and p = 1

slender walrus
#

,w solve (p^2 + p + 3)/(p-2) = 2p + 1

#

p=5 looks right
seems you messed up your other value

stable mirage
#

-1 mb

slender walrus
#

yes

#

that'll give you your points of tangency

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and you can get the respective slopes from the derivative

stable mirage
#

x and y
(5,30)
(-1,0)

#

x and y'
(5,15)
(-1,-3)

#

from there i solved for b in y=mx+b using m = y', x = x and y=y

slender walrus
#

how are you getting 15 and -3

stable mirage
#

2x+1

#

oh

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i used 2x+x

#

oof

#

2x+1 isnt working either

slender walrus
#

how are you getting the -45 and -4

#

did you update your calculations

stable mirage
#

nope

#

havent submitted

#

is this right?

slender walrus
#

just type -x instead of -1x

#

other than that, seems fine

stable mirage
#

no way broo

#

i hate webassign

slender walrus
#

ah right, they've explicitly stated smaller and larger

#

sry missed that part

stable mirage
#

dw

#

new randomization is the same question lets go

#

alr thanks for helping

#

.close

midnight plankBOT
#
Channel closed

Closed by @stable mirage

Use .reopen if this was a mistake.

midnight plankBOT
#
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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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acoustic owl
#

Question 23

#

I’m clueless

midnight plankBOT
midnight plankBOT
#

@acoustic owl Has your question been resolved?

midnight plankBOT
#
Channel closed

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#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

iron whale
#

im doing synthetic division and have reached (2x-1) as a divisor. do i just divide the binomial by 2 and continue?

last slate
#

u mean u got 2x-1 as remainder?

iron whale
#

no

#

im dividing by 2x-1

noble mural
#

can you be more specific id understand the question 💀

iron whale
#

$$(4x^4+3x^2-1) \div (2x-1)$$

grand pondBOT
#

CrEpasPmkinPie

iron whale
#

i need to use synthetic division

wary trail
#

show your working

last slate
#

^

wary trail
#

and tbh don't bother latexing anything

#

write it and take a picture

iron whale
#

my problem is that i dont know what to do with the 2 multiplying the x

#

do i divide the binomial by 2?

wary trail
#

okay, and we don't know where you are ar

#

at

#

so show your working

iron whale
#

i dont have work

#

thats my problem

#

i dont know how to start it

wary trail
#

then how are you asking this question?

mortal abyss
#

then go learn

#

maths

iron whale
#

this is review material for pre calc

#

and i never use synthetic division so i dont know what to do with the 2

noble mural
#

its very hard to explain synthetic division using text

wary trail
#

$(2x-1)\cdot 2x^3 = 4x^4...$

grand pondBOT
#

Xetrov

wary trail
#

start from here

#

but if you can't start it, go and read your notes

noble mural
#

u rlly should ask teachers or go watch it on yt ..

iron whale
#

i know what synthetic division is, ive used it, i just dont know how to do it with the "2"

wary trail
#

then we'll help you once you give us something more specific to work with

noble mural
#

keep dividing

iron whale
#

use synthetic with the divisor of 1?

#

ohh ok

#

thank you

#

thank you i got the right answer now

#

.close

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#
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umbral basalt
#

Hi, did I do the calculations correctly?

midnight plankBOT
umbral basalt
#

the teacher says that the correct answer is 2, because the assignment indicates to write a larger root in the answer

noble mural
#

i assume yes

#

cant find any faults

umbral basalt
#

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frank acorn
#

I'm reading a book that's supposed to help me catch up on math.
The book illustrates "Remainder's theorem" that says the remainder of the division between p(x) and d(x)=x-a is equal to p(a).

It says we can use this concept to determine whether a polynomial is divisible by another one, since it is divisible if the remainder is 0.

Then, next page, it's showing a way to solve this equation: x^4-4x^2+3=0

It says t = x^2, so we rewrite the equation as
t^2-4t+3=0

But now he says we can use the theorems studied on the page before, to rearrange the equation as follows:

(t-1)(t-3)=0

frank acorn
#

and this is what I don't understand

#

How did he go from
t^2-4t+3 = 0

to
(t-1)(t-3)=0

ornate cedar
#

Factoring

grim vector
#

Factor by roots

frank acorn
#

Has it anything to do with Ruffini's rule?

ornate cedar
#

What is that

frank acorn
#

maybe you call it differently

ornate cedar
#

Thats incredibly overkill for this?

boreal smelt
#

You find roots

ornate cedar
#

It's just rewriting the quadratic with its roots

frank acorn
#

Well, i'm not getting it, how do you do that?

#

What are roots?

#

Are roots the values that replaced with t would give 0?

grim vector
#

Ok so

ornate cedar
#

Do you know how to find them?

frank acorn
#

No! 😦

#

But still, I don't understand how he went from t^2-4t+3 = 0

#

to (t-1)(t-3)=0

#

I mean, I understand he did with roots, but how

#

I thought he used binomial identities

grim vector
#

When you find a root you can factor the polynomial as $(x- x_1)(x - x_2)$

grand pondBOT
#

YakuBros

frank acorn
#

Well, he didn't explain me this

#

Fucking book

grim vector
#

There is another form to the quadratic too which is the canonic form

frank acorn
#

He oonly said that Ruffini's rule says that if p(x) is divisible by a binomial x-a IF and ONLY IF p(a)=0

#

how is that going to help me

#

I don't understand

grim vector
#

Its explaining with many words that you can factor by (x- root)

frank acorn
#

Hm

#

I guess I'll have to look this shit myself online

grim vector
#

Bprp explain it well if you want

frank acorn
#

Im watching Brian McLogan on youtube

#

Link me any resource if you want

#

I'll watch it

#

.close

midnight plankBOT
#
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#
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last slate
midnight plankBOT
last slate
#

Not sure how to solve this waterloo contest problem

midnight plankBOT
#

@last slate Has your question been resolved?

twilit jetty
last slate
#

yeah

twilit jetty
#

how far are you on the problem

boreal smelt
#

I get 24

twilit jetty
#

its not 24

boreal smelt
#

Ok

#

Can you say what's wrong in my method?

twilit jetty
#

let pinner decide

boreal smelt
#

If I send it

#

Ok

last slate
#

tbh I’m lost as to where to start

#

you have to calculate for all possible cases like all 4 the same colour 3 the same colour etcc and add each

twilit jetty
#

it says that two circles colored by a straight lines may not be colored the same

#

you can count through the options that arent colored the same

#

theres very few of them

#

it helps if you assume that the top-left is "color A" and the top-right is "color B" to leave it general

#

theres also this dead-end here

#

its only connection is this other color, so its easy to choose a color for this dead-end if you leave it last

#

since its on its own too, once you select a color for the three-way, that allows 2 possible colors for the dead-end that cant be contested

last slate
#

That allows for the bottom left is c, then bottom right to be either b or a

#

vice verse for bottom right being c

#

and in both cars deadend can be a other a or b

#

Cases

twilit jetty
#

youre forgetting that the top-right is B

#

I think you should draw this

#

I also started considering cases in the bottom-left

last slate
#

Oh I see so if bottom left is c, then bottom right is a

#

and the deadend is b

twilit jetty
#

dead-end can be B or C

last slate
#

yeah

twilit jetty
#

remember you need to consider all cases, if you go through more of them per-search then its faster

last slate
#

Sounds good

#

so if bottom right is c, then bottom left is b and deadend is a or b

twilit jetty
#

there doesnt have to be a C

last slate
#

yeah

#

top left is a, top right is b, bottom left is b, bottom right is a and deadend is b or c

twilit jetty
#

thats also possible, yes

#

so heres what we've counted so far

#

(with color A being red and color B being green as an example)

#

in general, we counted this

twilit jetty
twilit jetty
#

so how many cases is that so far

last slate
#

3

twilit jetty
#

each of these 3 cases leave open the dead-end

#

so including the dead-end, how many cases is that so far

last slate
#

oh oops 6

twilit jetty
#

dw its a separate question

#

now with that, how many options do we have for choosing colors for A and B

#

remember that A and B are connected

last slate
#

When top left is A then top right is can be b or c

twilit jetty
#

no not like that

#

no

last slate
#

oh

#

like red green

twilit jetty
#

yea

#

I said to choose colors

#

not letters

#

youre setting A to be a color and B to be another color

#

thats why we went with A B C instead of just red green blue

last slate
#

If a is red then b can be blue or green

#

IF a is blue then b can be red or green

twilit jetty
#

...if a is green?

last slate
#

if a is green then b can be blue or red

twilit jetty
#

yes

#

so in total, how many ways can you assign colors to both A and B

last slate
#

6 ways

twilit jetty
#

yep

#

now A and B uniquely determine the graph too

#

so with 6 ways to determine A and B, and then 6 ways to determine the bottom of the graph, how many ways is that

last slate
#

48 ways

twilit jetty
#

6 * 6

last slate
#

36 ways

twilit jetty
#

there you go

last slate
#

mistake oops

#

thank you very much

twilit jetty
#

np

last slate
#

would it be possible to add you incase there any other questions i struggle with later on

twilit jetty
#

you dont have to ask me specifically but sure

last slate
#

okay sounds good

#

.close

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digital crag
midnight plankBOT
digital crag
#

how do i do thid

wary thorn
#

Can you show the question

digital crag
#

Use the Comparison Test to determine if the following integrals converge or diverge.

tribal tartan
#

compare it to the integral of 1/x

digital crag
#

why 1/x

tribal tartan
#

ln(x)<x

digital crag
#

but isnt it

tribal tartan
#

well we know that this inequality is true

digital crag
#

improper integral > divergent integral

tribal tartan
#

hence if we take the reciprocal it’ll flip around

#

yep

grand pondBOT
digital crag
#

oh u already did the cross multiplication

tribal tartan
#

if you have a smaller denominator the entire thing becomes bigger

marsh grove
#

Like how 1/0.5 is greater than 1/1

digital crag
#

Oh yeah

tribal tartan
#

and how 1/2 is bigger than 1/3

digital crag
#

Oh oh

tribal tartan
#

and hence if we compare it to 1/x

digital crag
#

I misinterpreted that

tribal tartan
#

our improper integral would be bigger than a divergent integral

digital crag
#

makes sense

#

Thanks

#

.close

midnight plankBOT
#
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cunning bobcat
#

how did that become that ?

midnight plankBOT
cunning bobcat
#

actually nvm

#

I got it

#

.close

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#
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sage helm
#

How would I prove that the limit doesn't exist rigorously?

sage helm
#

I mean I know that if I let m = n and m = 2n we have contradicting answers therefore it can't

#

But I need to be all "let epsilon > 0"

hard shard
#

there exists m >M and n>N for some arbitrary M and N in N right?

#

such that a_mn >0

sage helm
#

almost

hard shard
#

epsilon*

sage helm
#

N such that m, n

subtle blaze
#

less than!

sage helm
#

one big letter

subtle blaze
#

a_mn - a < epsilon

sage helm
hard shard
#

you want it to be greater than epsilon to showthe limit doesnt exist

subtle blaze
#

oh

#

oh right we want to do it doesn't work whoops

sage helm
#

epsilon cannot be made less than that

#

good enough?

#

@subtle blaze @hard shard

#

.close

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#
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hard shard
#

youre welcome

#

sorry i was watching a salt fork get made

sage helm
#

I will see the salt fork later too kekw

subtle blaze
#

it's really good

midnight plankBOT
#
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twilit field
#

Let h be a positive number compute the area under the curve 1/x between 1 and 1+h with the area of a suitable number of rectangles to show that

twilit field
#

$\frac{h}{1+h} < log(1+h)<h$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

zealous schooner
#

Oh this should be pretty easy

#

What have you tried

twilit field
#

yeah, just not sure whay they mean by a suitable number of rectangles here

zealous schooner
#

Probably two

twilit field
#

why not 1

zealous schooner
#

You can’t prove both an upper bound and a lower bound with just 1

twilit field
#

mhm

#

right

#

I first divide across by h

zealous schooner
#

$(b-a)\text{min}(f(x))\le\int_a^b f(x)\dd{x}\le (b-a)\text{max}(f(x))$

grand pondBOT
#

kheerii

zealous schooner
#

Where the min and max are in the interval [a, b]

twilit field
#

I don't "know" integrals yet

zealous schooner
#

Could prove it directly from this

zealous schooner
twilit field
#

I think divising across by h may help more actualy

#

divide the entire inequality by h

#

then I find the limit as h tends to 0

#

which would give me the limit to be 1

zealous schooner
#

Oh?

#

Are you talking about squeeze theoremv

twilit field
#

$\frac{1}{1+h} <\frac{ log(1+h)}{h}<1$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

twilit field
zealous schooner
twilit field
#

I mean using the squeeze theorm I can find the limit of the middle term if that's what you mean

zealous schooner
#

The squeeze theorem doesn’t work both ways

zealous schooner
#

What they intend you to do is just prove this geometrically

#

Draw the graph of y=1/x

twilit field
#

hmm

#

so I draw a rectangle from 1 to 1+h/2

#

and 1+h/2 to h

#

right

zealous schooner
#

Uhh, no

#

Both rectangles are from 1 to 1+h

#

On the x axis

twilit field
#

okay

zealous schooner
#

Their heights will be different, namely the minimum and maximum value of 1/x

#

In the interval [1, 1+h]

twilit field
#

so the areas will be h(1) and h(1/1+h)

#

right

zealous schooner
#

Correct

#

Now can you build an inequality from this?

#

Compare the areas

twilit field
#

$h<(h)/(1+h)$

grand pondBOT
#

ƒ(Why am. I here)=I don't Know

zealous schooner
#

Uh well, no

#

h > h/(1+h)

twilit field
#

right , my bad

zealous schooner
#

1 is the maximum value and 1/(1+h) is the minimum

#

But also I meant, compare the rectangles with the curve itself

#

Which rectangle has an area larger than the integral and which has a smaller area

twilit field
#

ah

#

right

#

h(1) has a larger area

#

h/(1+h) smaller

zealous schooner
#

Indeed!

twilit field
#

then I use the squeeze therom to compute the limit

zealous schooner
#

Is this part of a different question

twilit field
#

I meant the inequality

#

no

zealous schooner
#

You don’t need any squeeze theorem here

#

You just said the result you needed

zealous schooner
twilit field
#

oh right

#

I'm so used to limits xD

#

thanks

#

.close

midnight plankBOT
#
Channel closed

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zealous schooner
#

There’s a more general version of this as well

#

$g(x)\le f(x)\le h(x)\ \forall\ x\in[a, b]\implies\int_a^bg(x)\dd{x}\le\int_a^bf(x)\dd{x}\le\int_a^bh(x)\dd{x}$

grand pondBOT
#

kheerii

zealous schooner
#

Choose g(x)=(minimum value of f(x) in [a, b] ) and h(x)=(max value…) and you’ll get the previous result

twilit field
#

hmm,so integrals preserve inequalities

#

thanks

zealous schooner
#

Smth like that idrk

twilit field
midnight plankBOT
#
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royal mesa
#

hi

midnight plankBOT
hushed spear
#

hello

midnight plankBOT
#

@royal mesa Has your question been resolved?

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astral garnet
#

I just dont quite get what this is asking

midnight plankBOT
astral garnet
#

to me, C makes the most sense

#

if 2 non zero complex numbers are equal does that not imply their modulus and argument equal?

fringe onyx
#

not in the way you have it, no

astral garnet
#

hmm, is that because one could say have an argument that is a multiple of 2pi greater than the other one?

fringe onyx
#

yes

#

this is why we do branch cuts

astral garnet
#

logically i can deduce that D would also be incorrect too then

fringe onyx
#

correct

astral garnet
#

hmm idk about A and B though

fringe onyx
#

try to come up with counter examples

astral garnet
#

is the principal argument from 0 to pi/2

#

?

fringe onyx
#

definitely not

#

depends on the text book/prof

#

it will have at least length 2 pi

#

normally (-pi, pi]

astral garnet
fringe onyx
#

i think this is the standard

#

with rare deviations

astral garnet
#

then I think B would be incorrect, because we could end up with an argument outside the principal domain?

#

.close

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#
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spice scroll
#

is this the answer?

$H \in (A \rightarrow P(B)) \rightarrow (P(A) \rightarrow P(B))$

grand pondBOT
#

Ayanokoji

shy rampart
#

What does $H(f)$ return?

grand pondBOT
#

nameless individual

spice scroll
shy rampart
#

Suppose you have $f={(3,{5}),(5,{5,8}),(123,{5,8})}$, what is $H(f)$?

spice scroll
shy rampart
#

what is $<>$?

grand pondBOT
#

nameless individual

spice scroll
shy rampart
#

wait im confused right here

what is the $\times$?

grand pondBOT
#

nameless individual

shy rampart
#

nvm $f$ returns a set

grand pondBOT
#

nameless individual

#

nameless individual

spice scroll
spice scroll
spice scroll
shy rampart
spice scroll
#

thats although not neccarily true, also why im asking for help here

shy rampart
grand pondBOT
#

nameless individual

spice scroll
#

just what is

#

all im asking

shy rampart
#

$H \in (A \rightarrow P(B)) \rightarrow (A \rightarrow B))$

grand pondBOT
#

nameless individual

spice scroll
shy rampart
grand pondBOT
#

nameless individual

spice scroll
#

.close

midnight plankBOT
#
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bleak pier
midnight plankBOT
bleak pier
#

Orthogonal means AA^-t=I

midnight plankBOT
#

@bleak pier Has your question been resolved?

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dark jewel
#

I need help with the 19th question <@&286206848099549185>

buoyant slate
#

,rotate

grand pondBOT
grim vector
#

So y = sqrt[log(x)+y]

fresh sparrow
#

should be $y = \sqrt{\log(x) + y}$

grand pondBOT
#

artemetra

tough spindle
#

We can simplify to $y = \sqrt{\log \left(x \right) + \left(\sqrt{\log \left(x \right) + \sqrt{\log \left(x \right) + ...}} \right)} = \sqrt{\log \left(x \right) + y}$ and then write $y^2 - y = \log \left(x \right)$ and the rest is easy.

grand pondBOT
#

PowerUp

sinful trout
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and this is simply quadratic

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solve for y

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differentiate

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or whatever

grim vector
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Yeah

dark jewel
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okay thank you guys !!

fresh sparrow
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much much faster

dark jewel
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okayyy

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.close

midnight plankBOT
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midnight plankBOT
#
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rose cobalt
#

If $B=\bigcup^{\infty}{i=1} A_i$, then $\bar{B}\supseteq\bigcup^{\infty}{i=1} \bar{A}_i$. \
Give an example where this inclusion is proper.

grand pondBOT
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Ciceròn

zealous schooner
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Are you sure it isn’t supposed to be the other way around

subtle blaze
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what's the bar mean

zealous schooner
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Complement I presume

tender trench
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i would have thought closure?

rose cobalt
subtle blaze
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see that's why

rose cobalt
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its closure

subtle blaze
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we need to be sure

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i wasn't sure if it was complement or closure either

visual tiger
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it's closure yeah

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did you show the inclusion?

rose cobalt
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Yeah

visual tiger
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for proper example:

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consider the balls of radius 1- 1/n centered around 0

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(for R^d)

rose cobalt
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ohhh right

midnight plankBOT
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@rose cobalt Has your question been resolved?

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hollow thicket
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Two circles, whose radii are 12 inches and 16 inches, respectively intersect. The angle between the tangents at either of the points of intersection is 29°30'. Find the distance between the centers of the circles.

hollow thicket
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I did the math and got 8.11 inches, which is the correct answer.

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But...there is another answer which is 27.1 inches.

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I don't know where that came from.

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I used Cosine Law.

fresh sparrow
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show your work

hollow thicket
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a=12 in, b=16in, C=29°30'
c=distance between the centers of the circle

by Cosine Law
c²=a²+b²-2ab cos C
= 12² + 16² - 2(12)(16)cos(29°30')
= 144 + 256 - 384cos(29°30')
= 400 - 384cos(29°30')
c = sqrt(400-384cos29°30')
c = 8.11 inches

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why need to show work? i need an answer or maybe a hint on why there's another answer which is 27.1 inches

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or maybe it's just an error in the book???

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the problem is on number 12

midnight plankBOT
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@hollow thicket Has your question been resolved?

hollow thicket
#

<@&286206848099549185> ☺️

midnight plankBOT
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@hollow thicket Has your question been resolved?

last slate
last slate
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have you considered that that angle is the one being measured?

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giving you the angle in the triangle being 150.5

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150°30’

midnight plankBOT
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@hollow thicket Has your question been resolved?

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hollow thicket
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.reopen

midnight plankBOT
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hollow thicket
hollow thicket
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so like 180-29°30'? how and why?

inner gazelle
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is it geometry and trig?

midnight plankBOT
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sonic nova
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Hi! Can somebody help me understand question a? I have no idea how to solve it and I am in a bit of a hurry cause I have an exam tomorrow. I would really appreciate any help. Thanks! ^^

muted panther
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@sonic nova In order to find the matrix you want, you need to compute f(0,1,0) and f(0,0,1), as f(1,0,0) is given

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But (0,1,0) and (0,0,1) both belong in Ker(f)

sonic nova
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Can you explain in detail please? I have no idea at all T.T

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I am a little bit desperate. I don't need to fully understand it cause I don't have time but I want to know how to solve it. I have 8 hours till the exam 😅

midnight plankBOT
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@sonic nova Has your question been resolved?

wheat marsh
midnight plankBOT
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@sonic nova Has your question been resolved?

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After 15 minutes, feel free to ping <@&286206848099549185>.
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glacial fiber
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@midnight plank pls slove this math

midnight plankBOT
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Please don't occupy multiple help channels.

glacial fiber
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Ok

rose trout
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What have you tried? Since it's a graphical method, you should draw the lines and find their intersection.

surreal moon
midnight plankBOT
glacial fiber
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This math is correct?

surreal moon
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Also, bot will not help you