#help-23

1 messages · Page 338 of 1

earnest rain
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After

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Yes but I need integral pratice

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Need volume for it anyway

final loom
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I don't understand your variable substitutions. Did you use x = rcos t, y = rsin t, z = z?

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The limits then, for r would be [-R/h(h-z), R/h(h-z)], t would be [0, 2π], z would be [0, h/2]

earnest rain
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There is no x or y inside the integrals

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And t i put -pi/2 to pi/2 because it says x>0

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Why do you say r goes from negative? R is the radius so starts from 0

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<@&286206848099549185>

final loom
earnest rain
final loom
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Let me check

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The limits (-R/2) to (R/2) is for what?

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Shouldn't it be (-π/2) to π/2 if you substituted x = cos t, y = sin t

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You should be having $\ \int_0^{h/2} \int_{-\pi /2}^{\pi /2} \int_{0}^{R(h-z)/h} \rho , \cdot \dd \rho \dd \theta \dd z = \frac{\pi R^2}{2h^2} \int_0^{h/2} (h - z)^2 \dd z$

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@earnest rain

flat frigateBOT
final loom
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This'll give you 7πR²h/48

earnest rain
final loom
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Idek how you managed to send a "z" term to the denominator in line 2

earnest rain
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Its a 2

earnest rain
final loom
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Oh, and what's the limits -R/2 to R/2 for?

earnest rain
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Its h/2

final loom
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Oh

earnest rain
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The z limits

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Wait no

final loom
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But z limit is from 0 to h/2

earnest rain
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Its -pi/2

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Pi/2

final loom
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Hmm

earnest rain
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Its as u wrote

final loom
earnest rain
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Ye

hardy monolith
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,rccw

flat frigateBOT
final loom
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Denom should be 4

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@earnest rain

earnest rain
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Oh shit

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Thx

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.close

safe radishBOT
#
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mighty sandal
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hi guys!! me again. I really have confusion on how to make a venn diagram for these questions so can someone help me along with an explanation:

mighty sandal
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which might help me in future examples as well...

frail pumice
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So, in the Venn diagram, you have to draw 2 circles

mighty sandal
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yes and their intersection is 6

frail pumice
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Exactly

mighty sandal
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so, do I do:

only Caffeine= 8-6 = 2
only Sugar = 12-6= 6
Intersection = 6

6 + 6 + 2 = 14 -> Here is my problem

frail pumice
frail pumice
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But instead, there are 24 - 14 = 10 sodas that doesn't have either high amount of caffeine or sugar

mighty sandal
mighty sandal
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ohhh alright thank you so much

frail pumice
mighty sandal
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now, the next follow up is calculate the probablity that the soda picked at random is high in sugar and but not in caffiene

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so in terms of the venn diagram, would I need to calculate only Sugar

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or will the intersection count?

frail pumice
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And the question wants no caffeine

deep rapids
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jee type question

mighty sandal
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ohhh so it's a part of caffiene which the question doesn't want

deep rapids
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@mighty sandal u in 11th?

mighty sandal
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I'm in 10th lol

deep rapids
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oh cool

mighty sandal
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dream is IIT but...

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I'm really messing up in probability, set and venn diagrams

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also tysm for your help @frail pumice !!

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inland temple
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Hello, I understand all the working here, but I'm struggling to see why they decided to do the whole thing with u = sin(theta) instead of just using the double angle formula for costheta sintheta?

inland temple
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Is it just a matter of preference? How do I know when I should do the d(sin(theta)) thing?

vague slate
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If you go with double angle formula, you still gotta do a sub

inland temple
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Ah I see, thanks
So presumably once you get good at spotting it it's a useful tool

inland temple
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*normally

vague slate
inland temple
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Alright cool thanks

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.close

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:)

safe radishBOT
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fickle trail
safe radishBOT
fickle trail
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I don't understand the logic of f(x+h) how it suddenly becomes f(x+h)^2

fickle monolith
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it's (x+h)^2

hardy monolith
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they filled in f(x)=x^2

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f(x+h)=(x+h)^2

fickle monolith
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f(x)=x²
so f(x+h)= (x+h)²

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just replace x with x +h

lean otter
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If f (x) = x^2
Then f(x+h) is (x+h)^2

fickle trail
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f(x+h) - f(x) / h
we start with this

and i get that f(x) = x^2

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so f(x+h) - x^2 / h is also correct

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but if f(x) = x^2 why does f(x+h) = (x+h)^2

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we are just replacing x with x+h?

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thats all we are doing?

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putting a different input into the function

fickle monolith
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basically yes

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you can for example think of x+h as a separate variable

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to get more clear

fickle trail
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what if the function was f(x) = x^2 - h

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f(x+h) would be x^2?

fickle monolith
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no

fickle trail
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(x+h)^2 - h?

fickle monolith
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yeah

fickle trail
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hmmm

fickle monolith
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to get more clear, you can like assume u=x+h and substitute it into f(x+h)

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to see what's going on

fickle trail
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what about this?
f(h) = h^2 - h
(x+h)^2 - h

fickle monolith
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what?

fickle trail
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just different variable names

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not in this same context

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imagine it as a new question

fickle monolith
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i mean what do you want to mean in the last line

fickle monolith
fickle trail
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i'm not sure lol

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just trying to make sense of replacing inputs

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the bracket for a function is like a jail

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different from regular bracket

fickle monolith
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don't worry too much it's just change of input variables

fickle trail
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f(x) = x^2
f(x+h) = (x+h)^2

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hmmmm

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interesting

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i suppose that makes sense

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wow, that's a crapton of work that derivative power rule does so easily for us

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to find instantaneous rate of change for f(x) = x^2

plucky elk
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hopefully that means you'll appreciate using derivative rules and how much simpler they are

fickle trail
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yes

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they are amazing

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do we still use limits in higher calc? or no need

plucky elk
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yes

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limits are like the algebra of calculus

fickle trail
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ah OK, i was thinking limits would be used more for understanding correlation between average of secant to slope of tangeant

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i just learned difference of squares method by drawing out a 4 piece square today

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I would normally use FOIL on that

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FOIL prob faster, this looks like way more writing / drawing
but kinda cool to see it done this way

plucky elk
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that's equivalent to foil

fickle trail
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funny I never saw it explained like this until today

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been using it for years now

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almost feels like matrix algebra, maybe there is some correlation here

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btw, when someone says "Matrix Algebra" and "Linear Algebra", do they both mean exactly the same thing? if so, why the two names?

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or would there be subtle differences between both definitions

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kinda like perpendicular and orthogonal for example, 99% similar but tiny difference

plucky elk
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this has nothing to do with matrices

fickle trail
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oh

plucky elk
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tables look the same as matrices but have nothing to do with each other and you should just infer from context what it is

fickle trail
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Linear algebra is a broad field that studies vector spaces, linear transformations, and abstract mathematical structures, while matrix algebra is a subset of linear algebra that specifically focuses on matrices and their operations, such as addition, multiplication, inversion, and decomposition. Although matrices are a fundamental tool in linear algebra, the latter extends beyond matrices to more general concepts like vector spaces and eigenvalues. The distinction is analogous to the difference between a general theory and its practical computational tools.

plucky elk
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or ask

fickle trail
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now I gotta look up with "analogous" means

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`Analogous means that two things are similar in certain ways, allowing for a comparison between them. They share certain features, functions, or relationships, even though they might be different in other aspects or in their specific nature.

Analogous in Everyday Use: You might say, “A library is analogous to the internet in that both provide access to information.”`

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ty @plucky elk - always here to help 🙂

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safe radishBOT
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last falcon
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I can`t understand how to get rid of the root here

last falcon
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This is what I started with :

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,, \int\limits_{-\frac{\pi}{2}}^{\frac{\pi}{2}}{\sqrt{\dfrac{64,{e}^{\frac{8,x}{3}}}{9}+2,{e}^{\frac{4,x}{3}}}}{;\mathrm{d}x}

flat frigateBOT
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Ulerand

last falcon
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,, \dfrac{3}{4}\int{\sqrt{\dfrac{64{e}^{2u}}{9}+2{e}^{u}}}{\mathrm{d}u}

flat frigateBOT
#

Ulerand

last falcon
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Now I'm here, also u = 4x/3

hardy monolith
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notice that 64/9=(8/3)^2

last falcon
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Yes, but I can't really take it out of the root

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because of +2e^u

loud wren
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oh never mind

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i saw that

last falcon
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That?

loud wren
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or wait

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idt this is a perfect square case

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so factor an e^u

last falcon
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,, \dfrac{3}{4}\int{\sqrt{{e}^{u}(\dfrac{64{e}^{u}}{9}+2})}{\mathrm{d}u}

flat frigateBOT
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Ulerand

last falcon
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Like that?

loud wren
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yes

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now it looks uglier

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im stuck

cedar owl
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where did the bounds go

loud wren
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💀

last falcon
last falcon
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,, \dfrac{3}{4}\int{\sqrt{{e}^{u}}*\sqrt{(\dfrac{64{e}^{u}}{9}+2})}{\mathrm{d}u}

flat frigateBOT
#

Ulerand

last falcon
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If I could only get rid of the root at all..

empty gyro
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Maybe try $v=\sqrt{e^u}$

flat frigateBOT
azure delta
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If you sub v=e^u, you can follow it up with this

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Swr's suggestion might be easier though

last falcon
last falcon
flat frigateBOT
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Ulerand

last falcon
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,, \dfrac{3}{4}\int{v\sqrt{(\dfrac{64{v}^{2}}{9}+2})}\dfrac{2v}{{v}^{2}} {\mathrm{d}v}

flat frigateBOT
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Ulerand

safe radishBOT
#

@last falcon Has your question been resolved?

autumn kite
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have u tried taking e^4x/3 = v?

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@last falcon

last falcon
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So what about dx? Is it gonna be dx = 4/3 * 2v/v^2 ?

autumn kite
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wont dv= 4/3 ( e^4x/3 ) dx

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like factor out e^4x/3 in the original

last falcon
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Hm, maybe you are right in this one, yeah

autumn kite
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yea its coming like that

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the bounds look gay asf ngl

last falcon
autumn kite
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u getting it?

last falcon
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Not really, there still a root that stands in the way

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,, \dfrac{3}{4}\int\limits_{-\frac{\pi}{2}}^{\frac{\pi}{2}}{\sqrt{\dfrac{64,{v}}{9}+2,{v}^}}{;\mathrm{d}x}

flat frigateBOT
#

Ulerand
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

last falcon
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I can factor out v the same as I did earlier

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But it doesn't really gets me anywhere

autumn kite
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u get [64/9 v + 2] dv

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right?

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inside the root

last falcon
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dv right

autumn kite
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ye

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then again consider that term as t

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u feel me?

last falcon
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so like [64/9 v + 2] dv = t?

autumn kite
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ye

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not the dv part

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[64/9 v + 2]= t

last falcon
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ah

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,, \dfrac{3}{4}\int\limits_{-\frac{\pi}{2}}^{\frac{\pi}{2}}{\sqrt{t}{;\mathrm{d}t}

flat frigateBOT
#

Ulerand
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

last falcon
#

,, \dfrac{3}{4}\int\limits_{-\frac{\pi}{2}}^{\frac{\pi}{2}}{\sqrt{t}}{;\mathrm{d}v}

flat frigateBOT
#

Ulerand

last falcon
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and $t = 64/9 v + 2$

flat frigateBOT
#

Ulerand

autumn kite
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the limits change

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its not from -pi/2 to pi/2

last falcon
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Why so?

autumn kite
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do uk how to convert the limits when u use substitution

last falcon
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Aren't when u change the symbol from + to - ?

autumn kite
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no it changes

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limits change

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but in this case i wudnt wanna change the limits

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i wud solve this question indefinetly and then replace the value of t and then replace the value of v

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cuz like when we change the limits, it gets uglier

last falcon
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,, \dfrac{3}{4}\int\limits_{\frac{\pi}{2}}^{-\frac{\pi}{2}}{\sqrt{t}}{\mathrm{d 64/9v +2}

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,, \dfrac{3}{4}\int\limits_{\frac{\pi}{2}}^{-\frac{\pi}{2}}{\sqrt{t}}{;\mathrm{d} 64/9 v + 2}

flat frigateBOT
#

Ulerand

autumn kite
last falcon
autumn kite
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ye it explains why limits change

last falcon
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Okay, I guess I understand why it changes, tho I didn't really know about this

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But as u said, we can just do the indefinetly and then replace it

autumn kite
last falcon
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But the question is how to solve it even indefinetly

autumn kite
last falcon
autumn kite
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no the constant C wud surely make a difference

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we will get constants 2 times

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since we used substitution twice

last falcon
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Can't I ignore constant ? or what I shall do then

autumn kite
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see either we can change the limit twice

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or we wud need help from someone else regarding that indefininte integration constant stuff

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cuz im not sure waht to o

last falcon
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I never done const in defined integrals, even with the substitution, i just straight igored it and returned value (for example t) to x

autumn kite
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even i nvr faced the problem, since whenever i do substition i change the limits and it gets more simplified

last falcon
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I found this method of getting rid of root, but I don't really understand how it coud be. Like were the "2" before the e^u goes with the denominator and what +(0) is

safe radishBOT
#

@last falcon Has your question been resolved?

plucky elk
last falcon
#

Hmm.. I thought so, then I really have no clue how to deal with this

last falcon
#

aight, I give up on this one. Maybe another time

#

.close

safe radishBOT
#
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night bay
#

how to prove by mathematical induction that a polygon of n sides has n(n-3)/2 diagonals?

safe radishBOT
#

@night bay Has your question been resolved?

flint fiber
#

First you have to show that n = 3 is right

night bay
night bay
flint fiber
#

Ok, we need to find first a pattern how those diagonals really work

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This would serve as our basis

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For example,
3 sided = 0
4 sided = 2
5 sided = 5
6 sided = 9
7 sided = 14

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Can you see a pattern?

night bay
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yeah kinda

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what would the next step be?

flint fiber
#

What do you think is the pattern

night bay
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the only pattern I see is the diagonals have a difference of 2,3,4,5

flint fiber
#

Thats partially correct but specifically its diagonal of n+1 gon = diagonal of n gon + (n-2)

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So we will use this equation to continue our mathematical induction

flint fiber
#

So we need to show that its true for k+1

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So the equation would become (k+1)(k-2)/2

night bay
safe radishBOT
#

@night bay Has your question been resolved?

safe radishBOT
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rare vale
#

Can someone pls tell me what i got wrong here?

rare vale
#

there shouldnt be a +3la at the end

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it showed the answer earlier

rare vale
#

how is that wrong?

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Wait i see it

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i mixed up the terms lmao

#

thanks for pointing it out!

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lean otter
safe radishBOT
lean otter
#

I’m stuck

#

I’ve never had an equation with a division sign like this

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I’m trash

rugged arch
#

you can write it as 2L/6

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,, L + 2 = \frac{2L}{6}

flat frigateBOT
rugged arch
#

more familiar now?

lean otter
#

I kinda did that but I still suck

#

Cause the answer is 3 but I get 4

rugged arch
#

show work maybe?

#

2/6 simplifies to 1/3 so i’m guessing you got till $L + 2 = \frac L3$

lean otter
flat frigateBOT
lean otter
#

Is that incorrect

rugged arch
#

6 multiplies to (L + 2)

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u only multiplied it to 2

lean otter
#

L becomes 6L?

rugged arch
#

yes

lean otter
# rugged arch no

How do you avoid getting a negative answer? It keeps coming out negative

rugged arch
#

because the correct answer is a negative one

lean otter
#

That gives me an answer of 1. My thing told me L equals 3

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The answer sheet

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The question don’t even make sense though

#

Am I high or does that not make sense

lean otter
rugged arch
rugged arch
rugged arch
rugged arch
rugged arch
#

just write it out as follows:

Currently, denote lauren’s age as L and benjamin’s age as B

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in 2 years surely their age would’ve increased by 2

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so in two years, their ages are L + 2 and B + 2 respectively

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now use what your question says to form equations:

currently Lauren is six times as old as benjamin:

L = 6B

in two years, Lauren is twice as old as Benjamin:

(L+2) = 2(B + 2)

#

then solve those two equations simultaneously

safe radishBOT
#

@lean otter Has your question been resolved?

lean otter
#

It still kinda doesn’t not gonna lie

#

.close

safe radishBOT
#
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trail otter
#

is coposition of two monotonic sequences monotonic?

digital leaf
#

Yes,
One can look at the different cases easily
If u is nondecreasing and v is nonincreasing
x ≤ y
u(x) ≤ u(y)
v(u(x)) ≥ v(u(y))

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note that it works for any mapping, not only sequences

desert pasture
#

What about $a_x=e^{x^3}$

#

that isn't monotonic

flat frigateBOT
#

What a wonderful world!

trail otter
desert pasture
#

,w graph e^{x^3}

desert pasture
#

,w is e^{x^3} monotonic

desert pasture
#

huh

#

sorry

trail otter
desert pasture
#

yeah

digital leaf
#

Either u is constant or nondecreasing or nonincreasing

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Same for v

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So you have exhaustively 9 cases to study

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Study when u is constant, v constant
Then u constant, v nonincreasing etc

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I only wrote one of the nine cases, for u nondecreasing and v nonincreasing, but you easily see that the reasoning is similar up to changing the symbol ≥≤=

#

you first consider any value (or integer for sequences) x ≤ y
You then apply u, then v over this inequality
v(u( • )) is your composite of monotonic
if then v(u( x )) = v(u( y )), the composite is constant hence monotonic
If v(u( x )) ≤ v(u( y )), your composite is nondecreasing hence monotonic
and so on

trail otter
#

ah alright i think i see it now

#

thanks

safe radishBOT
#

@trail otter Has your question been resolved?

#
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lean otter
#

It seems wrong…

safe radishBOT
fathom adder
#

hmm

#

its 5 balls out of how many ?

lean otter
#

nvm actually, I figured it out 😅

#

.close

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merry herald
#

PCM problem solving, how do i start solving such problems

merry herald
#

the graph:

safe radishBOT
#

@merry herald Has your question been resolved?

safe radishBOT
#

@merry herald Has your question been resolved?

safe radishBOT
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@merry herald Has your question been resolved?

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bleak steppe
#

can you help me ?

safe radishBOT
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@bleak steppe Has your question been resolved?

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worldly umbra
#

J ai du mal avec la 4.b

safe radishBOT
worldly umbra
#

Car comment je peut en deduire ?

safe radishBOT
#

@worldly umbra Has your question been resolved?

worldly umbra
#

🙏🏻

rustic goblet
#

it's also a little hard because not everyone here speaks French

rustic goblet
#

ah, my bad

worldly umbra
#

But how can i translate all

rustic goblet
#

okay well, it sounds like you need to verify that $V_n = M^nV_0$?

flat frigateBOT
#

fallenstars

rustic goblet
#

okay, part 4a) states that $V_{n + 1} = MV_n$

flat frigateBOT
#

fallenstars

rustic goblet
#

I'll write a pattern out, and hopefully you can see the reason why 4b is true

worldly umbra
rustic goblet
#

\begin{align*}
V_1 & = MV_0 \ V_2 & = MV_1 = M(MV_0) = M^2V_0 \ V_3 & = MV_2 = M(M^2V_0) = M^3V_0
\end{align*}

flat frigateBOT
#

fallenstars

rustic goblet
#

see a pattern? catthink

worldly umbra
#

Yesss

#

But how do you know MV1=M(MV0)

rustic goblet
worldly umbra
#

Ahahaha yesss

#

A yesss

rustic goblet
#

V1 = MV0 comes from part 4a

worldly umbra
#

I didn't see this 😭

#

Thxxxx

rustic goblet
#

everything else goes by induction thumbsupanimegirl

rustic goblet
worldly umbra
#

Can i ask you a last thing

#

🙏🏻

rustic goblet
#

sure, but I can't promise to be able to answer kongouderp

worldly umbra
#

You can you are smarttt

#

I don't understand the 5.b

#

The start

rustic goblet
#

the problem is claiming that V_n = this matrix for all n in N

worldly umbra
#

express Un as a function of n

#

It's not already done????

rustic goblet
#

I'm not exactly sure what it means to express U_n as a function of n eeveethink

worldly umbra
#

😭

#

I use google translate

rustic goblet
#

nono, I understand what you're saying

#

I just don't understand the question

worldly umbra
#

Whyy

rustic goblet
#

maybe they want you to write U_n as an explicit vector

#

like they did with V_n

#

I'm not entirely sure kongouderp

worldly umbra
#

But it's already done?

rustic goblet
#

how is it done? pikathink

worldly umbra
#

😭

#

I'm confuseddddd

rustic goblet
#

why do you think it's already done? hmm

worldly umbra
#

@fathom adder can 🥲

#

Understand

fathom adder
#

haha

fathom adder
#

let me read

worldly umbra
#

😭

#

C est moi encoree

#

Désolée du dérangement

rustic goblet
#

Yakubros is here to say the day lisayay

fathom adder
#

haha

fathom adder
#

matrices sequences

worldly umbra
#

Ouii

#

Mais enft j ai pas compris

fathom adder
fathom adder
worldly umbra
#

La 5.b on nous dit d exprimer Un en fonction de n mais c est pas deja fait??

#

C est ça que je comprends pas

rustic goblet
rustic goblet
#

I haven't read French properly in quite a few years now

rustic goblet
worldly umbra
#

So It's a good exercise

fathom adder
worldly umbra
#

On la un peu exprimer en fonction de n?

fathom adder
#

Vn = Un - U

#

Un = Vn + U

#

tu as Vn

#

et tu as U

worldly umbra
#

Oui?

#

Enft c est je crois je comprends pas la question

fathom adder
#

pourquoi donc ?

#

exprimez Un en fonction de n

worldly umbra
#

Bah jsp ce que je doit faire

fathom adder
#

avant tu n'avais pas d'expression de Vn en fonction de n

#

sauf qu'il te la donne gentillement

worldly umbra
#

Un = Vn + U donc je doit trouver ca en fonction de n?

fathom adder
#

exactemement

#

surement que U est de la même forme que Vn

#

pour pouvoir faire la somme

worldly umbra
#

Petite question bete mais comment sait on que un c est ça

#

Genre juste en changeant me signe de u

#

Mais justement la question après ne suis pas

#

On me dit ma limite de an il y a pas de rapport

worldly umbra
#

Enft

fathom adder
fathom adder
worldly umbra
fathom adder
worldly umbra
#

A oui

fathom adder
worldly umbra
#

Mais ça doit etre penilble d exprimer Un en fonction de n

fathom adder
#

c'est quoi la valeur de U

#

?

worldly umbra
#

Att je retrouve la feuille

#

U(380,270)

#

C est ce que j ai trouvé

fathom adder
#

ok

#

et bien ajoute les deux matrices comme convenu

worldly umbra
#

Comment ça ?

fathom adder
#

Vn + U

worldly umbra
#

Att pour la 5.b?

fathom adder
#

oui

worldly umbra
#

Avec Un=Vn+U?

fathom adder
#

oui pour trouver Un en fonction de n

#

faut simplifier à droite

worldly umbra
#

Donc on remplace U par la matrice

#

Je remplace Vn par M^nVo?

fathom adder
#

non

#

par la valeur qu'il te donne

worldly umbra
#

Ahaha juste ça?

fathom adder
#

oui

worldly umbra
#

Aahahah

fathom adder
#

et après pour la suite c'est assez tout droit

worldly umbra
#

Donc j ai -100/30,8^n-140/30,5^n+380

#

Pour la première ligne dcp

fathom adder
#

en effet

#

et donc limite de an ?

worldly umbra
#

380

#

Dcp

fathom adder
#

parfait

#

je te laisse marquer la phrase de conclusion

worldly umbra
#

Et la question c ???

fathom adder
#

interprétation de limite

worldly umbra
#

On a pas deja conclu?

worldly umbra
#

Fin la c et la b c est la meme chose

fathom adder
#

la réponse est une phrase en français où le seul chiffre est la limite de an

worldly umbra
#

Oui

#

Juste ça pour la c?

#

Ça a l air trop simple

fathom adder
#

oui tu explique ce que veux dire le resultat de la 4b dans le contexte de l'exercice

worldly umbra
#

Oh ok

fathom adder
worldly umbra
#

C est simple alors

worldly umbra
#

Merci vrmt 🙏🏻

#

Tu me sauves toujours la vie

fathom adder
#

haha on est pas nombreux à parler français en même temps

#

pas de soucis

worldly umbra
#

D ailleur ça te prend pas trop de temps pour aider les autres?

fathom adder
#

quand je sais ce qu'il faut faire non

#

puis c'est comme je veux si je veux pas le faire je le fais pas

#

là avec gg trad pour un exo comme ça tu aurais galéré

worldly umbra
#

Oe j avoue

#

Mais c est chaud de traduire en anglais

fathom adder
#

surtout qu'on a parfois pas les mêmes visions sur les maths

#

y'a des choses qu'ils font qu'on ne fait pas du tout

#

et vice versa

worldly umbra
#

Oe c'est ça qui est nul

#

C'est dommage

fathom adder
#

des fois c'est pas plus mal

#

comme i = sqrt(-1)

worldly umbra
#

Oui?

#

Aaa oui

#

Nous c est ✓-1

fathom adder
#

nan nous c'est i² = -1

#

le probleme de racine de -1 c'est le symbole racine

worldly umbra
#

Oui?

#

Pas eux?

fathom adder
#

eux c'est ✓-1 justement

#

ce qui n'est pas à notre goût

worldly umbra
#

A oui je vois

#

Bon bah merci pour ton aide vrmt

fathom adder
#

ça marche, si tu as tout compris c'est bon pour moi

worldly umbra
#

Oui merci

#

Passe une bonne soirée

fathom adder
#

de même

worldly umbra
#

.close

safe radishBOT
#
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safe radishBOT
#
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tender horizon
#

Can someone please help me with this question

tender horizon
#

I thought of writing it out as steps

#

So for the 1st they could have gotten SSS (Scissor, Scissor, Scissor)

#

2nd they could have gotten RRR (rock, rock, rock)

#

3rd they could have gotten PPP (paper, paper, paper)

#

and 4th they could have gotten SRP (scissor, rock, paper)

#

I also know that there is a 1/3 chance of either choosing scissor, rock, or paper

#

but idk how to calculate the chances of losing/winning with this info

marsh walrus
#

So, you know the like

#

you know the total number of possibilities right

#

lets just think about 1 round

marsh walrus
tender horizon
#

cause 3!=6

marsh walrus
#

it seems like, take some person is first

#

they can choose 1 of the 3

#

then for each of those 3 possibilities, the second person can choose 1 of 3

#

and the same for the third

#

so for each of the 3, another 3, and then another 3

tender horizon
#

oh i thought you meant something else mb

tender horizon
marsh walrus
#

yea

tender horizon
#

and 27*4=108 total possible outcomes

#

cause there are 4 rounds

marsh walrus
#

before you go all the way out

#

do you know the probability that no one wins in the 1-round case

#

its not so bad to think out

tender horizon
#

Well there is a 1/9 chance two players pick the same thing

#

and there is a 1/3 chance the third player wins

#

so 1/27?

marsh walrus
#

hope the color comes through

#

not quite

#

does the layout of the diagram make sense?

#

this is a single round

#

i have a feeling im overloading the diagram

#

here's circled in blue all the outcomes wwhere no one wins

marsh walrus
#

6/27

tender horizon
#

You also have to include where all choices are different

marsh walrus
#

i have

#

oh, shit

#

i missed some

tender horizon
#

lol no worries

marsh walrus
#

so

#

9/27

#

how do you feel about that conclusion?

tender horizon
#

cool

#

So there is a 9/27 chance that they lose a single match

marsh walrus
#

no

#

there is a 9/27 chance that no one wins

tender horizon
#

so 1/3 chance

marsh walrus
tender horizon
marsh walrus
#

its not correct as the final answer

#

its correct for a single round

#

we need to use more thinking to get to the final answer

#

right, and were looking at a single match

#

you dont have to delete anything lol its all good

#

i should have maybe made it more clear the process i was gonna go through

#

than jumping right into numbers

#

It's important to agree that each round is independent, that's the last big thing

#

I mean, if someone wins some round, that doesnt change the outcome of the next round

#

it has no influence

tender horizon
#

yeah so we multiply all of the events up to get the ans

marsh walrus
#

if you win a round of rock paper scissors that doesnt make you more or less likely to win the next round

#

agreed?

#

you got it

tender horizon
#

yeah i agree

marsh walrus
#

,w (1/3)^4

tender horizon
#

thanks for breaking it down

marsh walrus
#

np

tender horizon
#

.close

safe radishBOT
#
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safe radishBOT
#
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Ask your math question in a clear, concise manner.
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After 15 minutes, feel free to ping <@&286206848099549185>.
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lapis breach
#

can someone please help me understand rieman sums and sigma notation

lapis breach
#

ill type out a specific question give me 1 min

#

im having trouble expressing it as sigma notation

#

right now im working on the midpoint

#

this is my understanding so far

#

I feel like i can do left ones

#

And probably right ones

#

but i keep messing up translating the difference between them

rigid inlet
#

The only major difference between them is exactly what the x_i are

lapis breach
#

yea ik that but how do i write that difference

#

in the sigma notation

rigid inlet
#

You divide your interval into n(=4) subintervals. The midpoint sum involves evaluating the function at the midpoint of each subinterval

#

Do you need to?

lapis breach
#

i need to write the sigma notation for the right left and midpoint

#

then plug it into a calculator and have the answers

#

professor didnt teach anything so ive been here for for 5 hours so far tryiung to teach myself

#

im at the point where i understand the concepts just dont know how to write it

#

i think

rigid inlet
#

I don't love what you wrote for M but the fact that decimals are included means that there isn't really a clean way to write it

lapis breach
#

well im not sure if thats right

#

i dont think it is

#

cause idk how else to represent that its a different x_n value

#

its x_0 = 1.5

#

x_1 =2.5

#

etc

#

right

rigid inlet
#

Indeed

lapis breach
#

so how do i write that as a sigma

rigid inlet
#

$\sum_{i=0}^3 f(x_i)$ with your list of $x_i$s is what I would do

flat frigateBOT
#

Steakanator

lapis breach
#

what does that mean

rigid inlet
#

What does what mean

lapis breach
#

why three and 0

#

i thought riemans always had to start with 1]

rigid inlet
#

You're the one who wrote x_0 = 1.5

#

Your index can start with whatever you want

lapis breach
#

yea but when i plug it into calculator it doesnt work

#

says its undefined

#

unless i use 1 and 4

#

or 2 and 5 etc

rigid inlet
#

Please show me exactly what you're putting into this calculator

lapis breach
#

i think i need to just start over again ive made no progress in my understanding

rigid inlet
#

I can't stop you but I'm not sure if such drastic action is needed

lapis breach
#

so wait if we go back to this one

#

would you be able to help me understand

#

how to go backwards from the sigma notation i have

#

back to the other parts

#

so i knownwhat part comes from what

rigid inlet
#

Keep this list at the front of your memory

lapis breach
#

okay

rigid inlet
#

$\sum_{x=1}^4 f(x)$ as you wrote is equivalent to $\sum_{i=0}^3 f(x_i)$

flat frigateBOT
#

Steakanator

rigid inlet
#

In the first we're moving through each number (which we can do since they're all integers and sigma notation is really meant for exclusively integers). In the second we're moving through each index

lapis breach
#

okay

#

so one is using the index names and one is using the actual values

rigid inlet
#

The second is f(x_0) + f(x_1) + etc. = f(1) + f(2) + etc. Because x_0 = 1, x_1 = 2, etc.

lapis breach
#

okay

#

so can i do it either way

#

writiing it via the index or writing it via the values

rigid inlet
#

Yes and no

lapis breach
#

how do I know when to use which

rigid inlet
#

You can do either way in this case because your values are integers separated by 1

#

The index form is universal

lapis breach
#

so ill always be able to use the index form?

#

in every case?

rigid inlet
#

In every case

lapis breach
#

ok so would you be able to teach me how to go from into the index form

#

so then i have a method i can apply to any problem

rigid inlet
lapis breach
#

okay 1 sec

#

okay so for this i see where the zero is coming from

#

why is it three should it not be 4

#

cause its looping through 5 different values

#

from index 0 to 4

rigid inlet
#

You're only covering left endpoints in that example

#

x_4 is the right endpoint of the 4th subinterval

lapis breach
#

so there is only 4 parts

#

that hit

#

on the left side

#

which indexes are those?

#

indexes 1 through 4?

#

indexes 0-3

rigid inlet
#

Those are the right

lapis breach
#

are the left

rigid inlet
#

0-3 are the left

lapis breach
#

Okay.

#

so x_4 = 5 isnt needed for this scenario

rigid inlet
#

Not for the left sum

lapis breach
#

so this is the left sum

#

because deltax is 1

#

cause 5-1/4 = 1

#

the right sum

rigid inlet
#

Having i as your sum index but x in the summand is bad form

lapis breach
#

what should i be

#

k?

rigid inlet
#

You need your variables to agree

lapis breach
#

so it should be 4/i+3?

rigid inlet
#

If you're summing through values of i then you need something involving i within your summand

#

Sure

lapis breach
#

so like this?

rigid inlet
#

There should normally be brackets around 4/i + 3, but since deltax is 1 it technically doesn't matter this time

lapis breach
#

ok

#

so now giuve me 1 second to write soemthign

#

Okay so now for this problem

#

to find the right left and middle

#

it would be this

#

correct?

#

cause same interval and n still = 4

#

so numbers should be the sam,e

#

for the left and right

rigid inlet
#

You really need to write the variable you're indexing through at the bottom of the sum

lapis breach
#

okay

rigid inlet
#

Because for L you've written the correct numbers for i, while for R you've written the equivalent values of x

lapis breach
#

wdym]

rigid inlet
#

5 is not an appropriate value of i

#

i stops at 4

lapis breach
#

how can you tell

rigid inlet
#

From the starting list

#

i is the index. Your index goes from 0 to 4

lapis breach
#

is the index not 0 --> 5?

rigid inlet
#

No

lapis breach
#

even though it says 1,5

rigid inlet
#

That is x

lapis breach
#

so i is the little number

#

x is the right side

rigid inlet
#

Sure

lapis breach
#

x is going from 1-5

rigid inlet
#

No

#

Yes

lapis breach
#

i is going from 0-4

#

so it should be like this

#

WAIT

#

it should start at 1

#

left excludes the last one

#

right excludes the first

#

so then how do i do the middle one?

rigid inlet
#

You need a different list, most simply

lapis breach
#

so it would be th9is right

#

left hand is the red

#

right hand is the blue

#

left side is the values right side is the index

#

but idk what to do for midpoint

rigid inlet
#

Again you need a new list

#

Your first subinterval is [1,2]. What is the midpoint?

lapis breach
#

would be this right

#

?

#

wait no it would be shifted down by one

#

starting at 0.5

#

is this correct?

rigid inlet
#

0.5 is not the midpoint of any subinterval

lapis breach
#

okay so the first one i had was correct

#

im just subtracting the left from the right yeah

#

@rigid inlet im looking for the index values of those right?

#

sorry im just really struggling to understnad

#

been working for hours

rigid inlet
#

Sorry I have to go, good luck

lapis breach
#

<@&286206848099549185>

#

!close

#

.close

safe radishBOT
#
Channel closed

Closed by @lapis breach

Use .reopen if this was a mistake.

lapis breach
#

.reopen

safe radishBOT
#

stoic dune
#

Those are the midpoints of the rectangles

#

Remember, you should have 4

lapis breach
#

why

#

like how do i figure out what those are

stoic dune
#

Break [1,5] into 4 parts.
Report back the center of each part

lapis breach
#

because n=4?

stoic dune
#

The 4 parts are
[1,2] [2,3] [3,4] [4,5]

Their centers are
1.5, 2.5, 3.5, 4.5

lapis breach
#

okay thanks so much

#

now how do i put that into a sigma

#

notation

stoic dune
#

Note that n + 0.5 gets those points, for n = 1,2,3,4

lapis breach
#

which is the right one

stoic dune
#

f(n + 0.5) is the height of each rectangle

#

1×f(n + 0.5) is the area

#

Where f is x² + 3 in this case

lapis breach
#

so are those generally true for all cases?

stoic dune
#

But, imo, if you're struggling, do it without sigma notation at first

lapis breach
#

i need to do it with sigma

#

because my professor told me to

#

she "taught" us integrals, sigma notation and this shit in 30 minutes and expected us to understand it all

stoic dune
#

Right. You definitely should work your way up to sigma notation, but it's a lot to learn all at once

lapis breach
#

I just straight up dont have time

#

class is so fast paced for no reason

#

but what do i do for the sigma cause it cant be 4 and then i=1

#

because thats already the R

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right one

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and it cant be 3 and i=0

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and it cant be i=0.5 and 4.5

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cause appearently you cant use decimals

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would this work

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cause its the same as the LEFT one

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but every i value is 1/2 higher

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@stoic dune

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ok so that is correct except it is 4 and 1 for some reason

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great now i gotta figure out how to do it with a table

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cause that didnt take me long enough

stoic dune
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First, identify the points. Which values of x are we sampling from?

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There's a table of 11 values there. We're going to use 10 of them

stoic dune
lapis breach
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we will be using the first 10 for the left

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and all but the first value for the right

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correct>

lapis breach
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im trying to make sure i understand sigma notation

stoic dune
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That is a way to write 1 + 2 + ... + 10 in sigma notation

lapis breach
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ok awesome

stoic dune
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This question is all calculation, and sigma notation won't be very helpful for this one

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Wait sorry, you want to write i, not xi

lapis breach
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why

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cause isnt i referring the the index

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and x is the value associated with the index

stoic dune
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i is the value, 1, 2, 3...

xi is some value that depends on i

lapis breach
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so for every value of i there is an x

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i is the index value no?

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x is the value that we actually care about

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right>

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the area under the curve

stoic dune
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xi is going to be the "sampling point". Left, midpoint, or right, depending on the question

lapis breach
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okay so i just found these formulas from my professor what is the difference between this and what ive been doing? Would it be easier to judt plug and chug using these for each type?

stoic dune
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No difference. Use which you feel more confident with

lapis breach
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i was under the impression that we have
x_i
x_0=1
x_1=2
x_2=3
x_3=4
x_4 = 5

lapis breach
stoic dune
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For the example above,
x1 = 0, x2 = 0.5, x3 = 1...

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It's where we "pin" each rectangle

lapis breach
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where each rectangle hits the graph

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at the left mid or right point

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right>

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would you be able to walk me through setting this one up

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so i can just know how to do it and can relicate that for future cases

safe radishBOT
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@lapis breach Has your question been resolved?

lapis breach
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no

safe radishBOT
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@lapis breach Has your question been resolved?

lapis breach
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Hello <@&286206848099549185> im working on trying to put this table of values into sigma notation so i can become more familiar with it. Ive gotten to the answer without it for this problem but using the formula above how do i get those values to put it in notation

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my k value would be 0

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my n value would be 10

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delta x = 0.5

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i believe those are correct but where do get the orther values

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Would this be as far as i can get without plugging in all the tables values in for a because im not explicitly told what f(x) is?

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well actually now ive just got to express sums in sigma notation regardless

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i guess id want to start by finding deltax

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which is 2

hoary saddle
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me before scrolling up knows whats going on

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a is just n+2
b is just n+4
c is just n+7
d is just 1/nx(n+1)

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or am i suppose to explain it idk

safe radishBOT
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@lapis breach Has your question been resolved?

lapis breach
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can u exolain how to do these

stiff kindle
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So, I assume you know the definition of left Riemann sum?

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or you can refer to it?

stiff kindle
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yeah so R_L I presume is the left Riemann sum. So can you write the problem in this form?

lapis breach
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yep

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i know how to get the k value and the n value obviously deltax is b-a/n but what is a

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oh i see

stiff kindle
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starting point

lapis breach
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is a the initial vlalye

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yea

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ok so i just plug all those values in and is that it

stiff kindle
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yep

lapis breach
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oh ok

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thanks

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im just so tired been doing calc fr 11 hoirs

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i shjould have been able to figure that one out

stiff kindle
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no worries, takes a bit to get the hang of it...

lapis breach
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yea its hard cause my professor desnt actually teach us anything

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so i gotta teach myself all of it

stiff kindle
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if you practice enuf times it'll come easy as it's not hard just need to get familiar

lapis breach
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yea

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i just keep losing track of what everything is

stiff kindle
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understandable

lapis breach
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cause im learning integrals sigma notation and rieman sums at same time

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and they all build off eachother

stiff kindle
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yep

lapis breach
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for this its just do area of square + triangle

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and do that for all the sections

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that it asks for

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displacement = area under velocity curve right

stiff kindle
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yes

lapis breach
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dude calc 2 is so much harder then calc 1

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i mean i think ts also cause my professor sucks but like calc 2 just seems like more stuff to remember and formulas and stuff

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well ig thats calc 1 also with derivatives

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but

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idk

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just seems less intuitive

stiff kindle
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yeah integrals are probably more hairy although it depends I guess. It's worth grinding it out, it will all be second nature. Every one has to go through it 😅

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Intuition often times comes with practice as well.