#help-39
1 messages · Page 140 of 1
can't say for sure
or 0/1
the answer does not exists, but it has nothing to do with t=0 is undefined
then
which jst leads to 0
so do i need to factorize
to find out if it dne
the problem here is that the expression is like infty-infty, so you can't say that it DNE {for sure}
you have to do some mathematical work to say anything here
its 1
how do yk
oh
my bad
so the value of the limit dne?
it is infinity-infinity form but the limit isnt 1
i got 0
then 0 is the limit
i dont get it
u dont get what
how its solved
how did you got 0?
u just said u got 0, how did u get it without solving?
factorized
but im not sure if its correct
can you show the work?
show your work
or explain how you've done it
i cant
ok
i think i did it wrong
the second term overtakes the first term, so it is -infty. t≤0 makes no sense, so this is limit from the right.
better work with t
thats not how a limit is solved
then how is it solved
also are you sure in the question its t^(2+t) and not t^2 + t
yes
i dont get it
1/t^2 goes to infty faster than 1/t
so whats the final answer
how
by replacing 1/t^{2+t} with something nicer
It is more clear to see, if we combine both the fractions.
then we can directly plug in the 0, to figure out the answer
only you can
we can't hand out the answers
but we can lead you to the answer
ok
technically we mentioned everything you need, you just need to put them together
so the answer dne because the limit is 0
🤦♂️
just start by combining the fractions 1/t and -1/t^(t+2)
0
you can multiply $\frac{1}{t}$ with $\frac{t^{t+1}}{t^{t+1}}$
Hugaxi
to get common denominator right?
how so
its supposed to be
1/t - 1/t(2+t)
ok you still have to combine fractions
ok i will try now
maybe factorize t in 2nd fraction
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Hi, can someone help me how do I ~~crossout ~~ strikethrough text in an equation? I just can't find any way to do it and no guides seems to give a comprehensible explanation on how to do it (functions and buttons are not where they say they are etc).
@peak steeple Has your question been resolved?
@peak steeple Has your question been resolved?
not sure what you mean
You mean to crossout text? I guess it's called "Strikethrough", that word came to mind now.
How do I strikethrough text in an equation in Excel?
I want to strikethrough so that I can show which variables are cancelled out, and how, in my calculations.
Go into format text
Try Ctrl+5
Thank you, but that doesn't work in equations unfortunately
@peak steeple Has your question been resolved?
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@peak steeple Has your question been resolved?
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hello im having issues with the second question of this problem
i'm not exactly sure what it really is asking for
@arctic carbon Has your question been resolved?
Yea it's a weird question
Arc length = r * theta where r is radius and theta is the angle in radians
yeah i converted that at the top
From theta, find (x, y) using trig
Your r isn't correct
alright
The question says unit circle
Yes
ohhh
so i find theta
with the given s and r
theta = 3.7?
but i need to convert to degrees now
You don't if you use radians
,calc sin(3.7)
Result:
-0.52983614090849
,calc cos(3.7)
Result:
-0.84810003171041
just did it again in my calculator i did something wrong on the calculation
this is the right one
okay so (-0.848..., -0.529...)
will be my coordinate
.close
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@ripe panther Has your question been resolved?
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can someone explain to me how can that polynomial be written as that summation?
All polynomials can
how?
You mean the sum?
yea
What do you think a polynomial is
i know what a polynomial is
What is it then
an expression with variables and their coefficients
those variables can be of varying degrees
That's not very precise
i guess what i specifically don't understand is why is Z raised to k there
this was a stupid question... i get it now
i was confused because since z is the root as written there, i thought why would you have z with every coefficient
i think i am lagging?
oh fine
it was my first time seeing this form i got confused
.close
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i understand the sin(x) and cos(x) but not the 1 and the tangent (like how does it make sense), can someone explain?
tan = sin/cos, right?
notice that you have similar triangles
the smaller one has side lengths sin(x) and cos(x)
and the larger one has side lengths ??? and 1
their ratios are the same, so:
Two triangles are similar if the three sides of one of them are proportional to the three corresponding sides of the other.
ok i get that they’re proportional but i dont really understand they rest you’re saying
do you agree that the horizontal side of the small triangle is cos(x) and the vertical side is sin(x)?
yep
ok and the horizontal side of the large triangle is 1, right?
yup
okay
ok good
now we want the vertical side of the large triangle
say we call that y
now do the side ratios and set them equal (since they are similar triangles)
for the large triangle we have y/1
for the small one we have sin(x)/cos(x)
set them equal
you get y = sin(x)/cos(x)
so your unknown side is sin(x)/cos(x), which is tan(x)
cool
so it won’t matter if its cos/sin right
if you do the ratios the other way you mean?
you have to equal to 1/y then
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Hey
Im trying to resolve this
And i get to this:
The problem is that the book, says that the unique solution is 3
But even testing the equation with the gives me a bad result:
okay nvm i did calculate bad
Look again at what you did from the second to last to the final line.
mmm
what do you mean?
I believe that there is a mistake in that step.
In the second step?
Oh never mind
Applying the discriminant rule, I do get D = 0, so there only exists one solution
But why do I get 21/4??
The act of squaring both sides produce that extraneous root
And how do I solve it without squaring both sides?
How do I get that radical out?
I don't think there is any other easier method than solving by your way
So everytime I resolve a quadratic, I have to apply the discriminant rule, and based on that, always check the results?
erm yeah ig
or you can just plug the root in original equation to see if it satisfies it or not
wdym?
like substitute 21/4 in the original equation
and compare the both left and right hand sides
yeah, that's what I did, and It doesn't satisfy so that's why I came here😂
Okay, so always I do a quadratic I have to check the solutions
right?
whenever you square both sides in any equation, yes
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does this seem correct?
@mossy halo Has your question been resolved?
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g^-1(e^x) = t
e^x = g(t)
e^x = g' dt/dx
dx = g'/e^x dt
I subbed this yeah cause I dont see how to get g^-1 anyway
Soo
I go back to the original integral
And write g^-1(e^x) as t
And the derivative of it
I do $g(g^{-1}(e^x)) = e^x = g(t)$ and take the derivative of that instead
bacc
,, \frac{\dd}{\dd x}e^x = \frac{\dd g}{\dd t} \cdot \frac{\dd t}{\dd x}
My brain is not braining
bacc
One very crucial property of inverse functions is $$f(f^{-1}(x)) = x = f^{-1}(f(x))$$
bacc
I Didn't know that one
what
Well that's bad
So basically I can write e^x as g(g^-1(e^x))?
,, \int_{e^0 = g(t)}^{2e = g(t)} t \cdot e^x \cdot \frac{g'(t)}{e^x} : \dd t
bacc
bounds were from 0 to ln(2e) so we need to change them in terms of t
yes
And the derivate of g^-1(e^x) is g'(g^-1(e^x))
Yep
But we dont want it cause it involves g^(-1) and we simply cannot use it because we cannot calculate it algebraically
Got it
Let
\begin{align*}
g^{-1}(e^x) &= t \
\Leftrightarrow g(g^{-1}(e^x)) &= g(t) \
\Leftrightarrow e^x &= g(t) \
\end{align*}
Now you differentiate both sides and get $$ \frac{\dd}{\dd x}e^x = \frac{\dd g}{\dd t} \cdot \frac{\dd t}{\dd x}$$
which is basically $$e^x = g'(t) \cdot \frac{\dd t}{\dd x} \Leftrightarrow \dd x = \frac{g'(t)}{e^x} : \dd t$$
bacc
We can work with g'(t)
e^x gets cancelled nicely
Now we only need to also change the bounds and that's it
How did you get d/dx e^x? Sorry we aren't really taught this
Differentiating both sides wrt. $x$ means we apply the differential operator $$\frac{\dd}{\dd x} ( : )$$
bacc
This is basically like implicit differentiation
Got it
,, \frac{\dd}{\dd x} ( g(t) ) = \frac{\dd}{\dd t} ( g(t) ) \cdot \frac{\dd t}{\dd x}
bacc
g'(t) t'
I actually think we don't
I think we just ignore them and rather resubstitute
after we are done
@loud juniper Has your question been resolved?
Alright thx
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to see if i understood, is this correct?
yep
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So I've solved this
just wanted soln verifeid
I started by dividing the numerator and denominator by (x+2)
to obtain
ykw
(x+2)(x-1)
not just x+2
exactly
so a=-3
idt that works
Note that you need it to be 0/0
how are you getting these
That works, and will probably give you some insight on how the function looks like, but I think neon tried to suggest a more direct approach
You wanna make sure x=-2 is also a root of the numerator
Well even if you do use the factor theorem you're gonna use the fact that f(-2) = 0 anyways
well
Your approach is to long divide and set the remainder to 0 right?
feel free to do the long division thing, but just a tip: if this was on a test, you should just choose the easier approach, unless you are really confident that you have enough time to do the possibly more insightful approach
yup
so (a-3)x+(a-3) is the reminder
I'm pretty sure it's not
you are dividing numerator by (x+2)?
I think that it will complicate things even further
wolfram doesnt like it when parameters
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,w long divide (3x^2 + ax + a + 3)/(x^2 + x - 2)
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Yeah
when I think about it, it would probably look ugly
yeah, that'd bad
but after dividing it by x-1 it will be
this is extreme overcomplication
,w factorise x^2+x-2
oh
MæthIsAlwaysRight
this is what I got
Btw, i think this path is not a good one to take
oh
even if you had this, how would you continue?
you are essentially asking for more than you need to here
yeah
if you ask for the remainder to be 0, you are asking for the function to be constant (f(x) = 3)
I'll use the other methof
and it will never be
No, you arent
you are just overcomplicating stuff, even though you are aware of simpler solutions
you should be more lazy sometimes lol
did that while preparing for entrance exams
not doing that again
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I meant lazy in sense of looking for simple sols
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Anyone help
I used Pythagoras and it still wrong
2020 squared plus 2000 squared
And square root that I get 2842.6
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part b

f^-1(x)=sqrt((x+3)/2)
Then set it equal to f(x)
i did and got weird numbers
i havethe working but i dont understand it
want to see it?
Ok what did you get
Ok
Plug in that value into f(x) and f-¹(x)
i didnt finish it cuz it looked sketchy n gave up
Why did you set f(a) =a
tahst what i dont get too
its gives the same answer?
i mean i did that but i got inverse powers
ill try again
,w plot -sqrt((x+3)/2) , 2x²-3
sorry i attemptyed and i acvtually have no clue what i ended up with
Damn
u tried to equate?
Result:
0
@heavy token
Ok
@heavy token Has your question been resolved?
ill close this, ill continue solving the equation u ended up with
thanks
X=-1 is a root
Then you can use polynomial division to get the other factor
And solve for other roots
,w plot 8x^4 - 24x^2 -x+15
Then check which values lie in the domain of f and f-¹
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@safe lance Has your question been resolved?
Show the orginal question
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Hello, I am very confident on my answer to question 1, since the third column in matrix A is the only one indicating no change in Z position (matching with rotation T), and the second column in D is the only one indicating no change in Y position (matching S). I did matrix multiplication to solve for ST and TS and assigned them to the corresponding matrices
--
I am not sure if I am missing something with question 2, though, since I originally got TS through computation, and it feels like I am supposed to have a more complex answer to the second question
I might be mistaken, though, and it may just be a straightforward question
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<@&286206848099549185>
@slender lake Has your question been resolved?
.close
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@safe lance Has your question been resolved?
A parallelogram ABCD has vertices with coordinates A, B and C at (1, 0, 3), (-2,3, 4) and (3,2, -6) respectively. Find the coordinates of the point D.
@safe lance Has your question been resolved?
@safe lance Has your question been resolved?
@safe lance Has your question been resolved?
AB=(1,0,3)-(-2,3,4)=(-3,3,1)
BC=(-2,3,4)-(3,2,-6)=(-5,1,10)
D=(x,y,z)!
(x,y,z)+AB=C
(x,y,z)-BC=A
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Hello
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A clothesline is tied between two poles, 8 m apart. The line
is quite taut and has negligible sag. When a wet shirt with a
mass of 0.8 kg is hung at the middle of the line, the mid -
point is pulled down 8 cm. Find the tension in each half of
the clothesline.
I drew an x-y plane where the clothesline is the x-axis and the y-axis as the middle of the clothesline
<@&286206848099549185>
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can someone get an answer pls
i just dont know if mine is corect
since i dont have answers
is the z here a complex number
ok so what do you need to find exactly?
uhm
solve for z
wait i think
perhaps my teacher
wrote it wrong
cos it seems there are no solutions
yea there are none
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Just looking for a explanation really, this is about probability. Without translating the whole question im just gonna give the numbers and the question itself.
$P(A)=0.1$, $P(B)=0.2$, $P(A\cap B)=0.05$.
What is the probability that the item has exactly one of each error A and B?
Totalani
nevermind I got it, add prob of having A and not B, and prob of having B and not A, togheter
.close
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Question one. I plugged in the formula and got 10x but did I do that correctly??
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bruh!
^this btw
ok so what am i supposed to do then
did i use the formula correctly
Idk this is what I did
@lusty magnet Has your question been resolved?
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how do i write this as piecewise function? i'm confused
A school's fair committee wants to sell t-shirts for their school fair. They found a supplier that sells t-shirts for ₱165.00 apiece but can charge ₱15,000 for a bulk order of 100 shirts and ₱120.00 for each excess t-shirts after that. Use a piecewise function to represent the cost in terms of the number of t-shirts purchased.
||/|| 165x, for x < 100
f(x) = { 15000, for x = 100
120x + 15000, for x ≥ 100
do u understand my function 😭
x = no. of t-shirts
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I need help in findign
how do i find a-sub1
in an arithmethic/harmonic sequence
i already have the D ( common difference)
and a4 and a6
what formula should i use in fidning a1? without substracting a4 to a1 to find it
ik an = a1 (n-1)d and all that but what woudl i replace (an) to find (a1)?
@cunning compass Has your question been resolved?
Substitute n=4 and n=6
This way you have a system of 2 equations in 2 unknown (i.e. d and a1)
You only need the formula $a_n = a_1 + (n - 1)d$
Alberto Z.
Forst you sub n=4, and this is an equation
The other equation is the one you get subbing n=6
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Hello, I need some help with interpreting a multivariable integral
Consider an arbitrary function, F(x)=y. A way of interpreting the average of this function F, is to multiply F by x and find the integral of that.
But then, consider the arbitrary multivariable function, F(x-y)=z. If I were to use the same method, (mutliply F by x, and find the integral) would that be interpreted correctly as the average of F? If not, then what can it be interpreted as?
Does a method where I multiply F by both x and y and find the double integral of that, give the average of F?
@cerulean quail Has your question been resolved?
Mhm! a double integral with F(x-y) and its bounds would give u the average of F
also a triple integral with F(x,y,z) bounds would give u the average of it
it’s basically the same principle
but to get the average of F, u will have to take every x, y, z variable from its lower bound to its upper bound and put them into the function F to get the final result
it’s basically taking the sum of everything you get from integrating the F(x,y,z) under every condition
I suspected that, thank you. However, in real life, my function really is the integral of F(x-y)x. Is there any interpretation of that? Actually, maybe I could use integration by parts, or something.
That problem, is that I cant introduce y through the integral. I can introduce dy though.
If the function is already the integral of F(x-y)x, then its not the average of F, the average of F is just the regular F with no x variable in it
yeah, then that doesn’t measure the average of F because you’re gonna integrate F under condition of x-y
the same way if you said F(y-x) the average would change)
i am a bit confused, what do u want to know about this F? are u looking for the area under its curve?
because F is undefined and the way its gonna be used depends on what u want to know: the average of F or the area or smth else
Yeah, I just realized I have no definable bound for y anyway.
if u are looking for the average of F, then u need a function F without any variables, just a simple plain normal F
because when u integrate F, whether F is F(x-y) or F(y-x), it’s gonna be the same result
but the average is going to be different
I was trying to simplify some stuff, and that integral came up. Its the only thing that I didn’t know how to further simplify, but it looked like taking an average.
I thought that the average of a function, F(x)=y, is the integral of F(x)•x.
in the single variable case, theres another way to interpret integral xf. its one of the factors used to find the “center of mass” if f represents density. more specifically x_c = integral xf/integral f
the center of mass formula extends to multivariable
So another way of understanding an average is interpreting it as density? The thing I was doing irl more resembles density than averaging, so, hmmm.
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here M=integral f
not density directly but smth proportional to center of mass
Wow, that’s very interesting. My thing is a coordinate. Yeah, its part of the equation to a center of mass.
Not actually irl, i meant that I see it that way now
Thank you a lot
no prob!
I remember learning this in calculus years ago, and never really paid much attention to centers of mass. I’m glad it finally was relevant to something!
My question is resolved.
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So as $v_1,v_2,v_3,v_4$ form a basis of $V$ . They are all linearly independent. Thus ,in $U$, $v_1,v_2$, are LI too.
Veni, vidi, perii
Now every element in $V$ is spanned by $v_1,v_2,v_3,v_4$. If there exists a subspace of V that doesn't have $v_3,v_4$ . It won't contain any scalar multiple of $v_3,v_4 $ either, and thus none of the vectors spanned by them. . Thus, it will contain all vectors of the form $av_1+bv_2$.Thus $U$ must be spanned by $v_1, v_2$.
Veni, vidi, perii
and thus none of the vectors spanned by them
why?
if it doesn't contain v_3,v_4. It can't contain any of the vectors spanned by them
uh
that's not how it works
"if v and w in U, then av+bw in U"
that's U being a subspace of V
yes
A => B
I know
it should be not B \implies not (A)
does this have a lot of chance of being true everytime?
the contrapositive is this
the reasoning you used is this
oops
alright so
if your reasoning doesn't work everytime
maybe it's worth looking for an example of
where it doesn't work
I mean I can just identity what not B and Not A are
you've asserted
"v3 and v4 are not in U, thus no linear combination of v3 and v4 is in U"
first of all that's false with vector 0
but it's not a counterexample we're looking for
can you find an example for U
such that
you do have a linear combination of v3 and v4 in U
but neither are in U
(hint : think U = span(v1,v2,...))
Other than the 0 vector, no
OK. I'll prove the contrapositive
If $v_1,v_2$ aren't the basis of U. Then $u_1 \notin U \vee u_2 \notin U \vee u_3\in U \vee u_4 \in U$
Is this right?
wait what
the contrapositive is if (v1,v2) not a basis then v1 not in U or v2 not in U or v3 in U or v4 in U
ah
Veni, vidi, perii
it's still gonna be hard to prove something false
go back to the original statement
okat
and try to find a counterexample
okat
so U such that
so there is a counter example
I mean every spanning list can be reduced to a bases
yeah but we don't know a spanning list of U yet
we do know a LI family of U tho
first of all
what's the dimension of the U we're looking for
My point though is that u_1,u_2,u_3,u_4 are LI
yes
.
2?
if it were 2
then (v1,v2) is LI in U
and has two vectors
so it would be...
LI?
already said
you have a LI family with exactly dim(U) number of vectors
I don't know any properties of dim
so v_1,v_2 is a basis
when dim(U) = 2
yes
did we say dim(U) needed to be 2?
no
alright
so we have to check if it's possible for other dimension values
what are the other possible values for dim(U)
3 and 4
These don't form a basis
again you didn't get the point
we're trying to find a counterexample
so for instances where (v1,v2) is not a basis
given v1 and v2 in U
and neither v3 nor v4 in U
if dim(U) = 4, is that possible
I mean it would prob be (v_1,v_2,v_1,v_2) for instance
(v_1,v_2,v_1,v_2) is a basis now?
no
ok
ooo, me likes this exo, me joins
what dim is V
4
so U and V are the same dim (same size)
yes
Yeah, so dim(U)=2
3
nuh uh
we've shown dim 4 is impossible
but that doesn't mean dim 2 is the only possibility
Why do the two vectors that are linearly independent in U span U, then?
dim(3) would mean that the basis are either (v_1,v_2,v_3) or (v_1,v_2,v_4)
why?
can't I complete (v1,v2) into a basis that doesn't contain v3 or v4?
for example
if you combined v3 and v4
and only put their combination as third vector of a basis...
Btw, try not using "the basis", unless you are talking about one specific established basis
then v_4+v_3 would lie in U
but v_4, v_3 don't
?
we're combining v3 and v4
not v1 and v3
make U have a basis (v1,v2, combination of v3 and v4)
for example... v3 + v4
Remember that in itself doesn’t really mean much, considering…
…here
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for part C) would the answer be China or India? China increases a lot (about from 1 to 11) but India goes from like (0 to 2.5)
and for part D) do I add together (all others, China, and the US)?? or do I not include "all others"
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How do I decide which expression is meaningful?
i assume these are vectors and that . means dot product?
yes
any thoughts about any of them?
sadly there are several that are not
remember that you can only take a dot product of two vectors
you can't take a dot product of a scalar and a vector
for example:
scalar product must be applied on a real number and a vector
dot product must be applied only on 2 vectors
vector addition must be applied only on 2 vectors
there's another one that is invalid for a different reason
can you add a scalar and a vector?
yea
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a = v* dv/ds
so does that mean a = 5 sin 3x * 15cos 3x
and idk what to do next with that
<@&286206848099549185>
shouldn't that be dv/dx, since i see no s
use double angle identity of sine
and since there is no 2 in the coefficient, jus diovide by 2
oh so a=(5sin(3x)).(15cos(3x))=75sin(3x). cos(3x)
ueah
yess
and that's about it
thanks a lot
sis jus close this
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Help with part a plzzz
@tiny wadi Has your question been resolved?
@tiny wadi Has your question been resolved?
nvm I've done part a
could anyone help me with part c
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May I acquire some assistance on my physics homework I just started speed and velocity but we had substitute and he barely went into detail and just gave us worksheet
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I was wondering if I did this problem correctly.
A steel rod of length L cm has variable cross-section area A(x) cm^2, where a is measured in centimeters from one end of the rod. The rod has uniform mass density p g/cm^3. (a) Using Riemann sums, derive an integral for the total mass of the rod M. (hint: divide the rod into n slices, find the mass of each slice, ...) (b) Compute the total mass for the case L = 25 cm, A(x) = (1+sqrt(x)) cm^2, p = 8 g /cm^3. Express M in Kilograms
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can someone break down this question for me
I'm not sure what its asking
I looked up what cummaltive sum is
and it seems to be an array where each element is the sum of the previous elements
but is says a die is being tossed repeatedly
does that mean its being tossed an infinite amount of times?
oh
hmm
I see what its getting at now
i guess it is tossed until you either reach or exceed 20
in any case, a finite number of times
yeah thats what I was thinking also
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how to do this?
A/(x-2) + B/(x-2)^2 + C/(x+3) + D/(x+3)^2
what to do after this
this equation that you wrote equals the Numerator
and try to get how much does A,B,C,D equals
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How would I tell if two vectors are parallel?
Is there any way that's related to the dot product?
Because cross product is in the next chapter
And if the dot product is not equal to the product of their magnitudes, would this mean that the vectors are not parallel aka either orthogonal or neither?
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How is this wrong
So the >=3 is inclusive, which means that exactly at 3 or more you'd use the bottom formula
4x - 12
4(3) - 12 = 0
uh no it's asking for g'(3) not g(3)
The derivatives at both ends don’t match
U have to evaluate the derivative of both functions
oh I see, my bad
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Please format your response and provide clear thought-out explanations.
Q: When graphing a quadratic, what numbers would be assigned to the X and Y values? Or do both values receive all given ammounts (x being both x and y)?
1. I am confused regarding how this is equivalent. If quadratics are functions that apply various operations such as addition to an input value of X and the goal is to find the zeroes to describe/graph their behavior on a 2d plane via x and y coordinates then how is it that you can remove some of the operations (subtracting c/a) if they were apart of the behavior they were trying to graph?
Additional Prompt: Please describe how one would come to the conclusions given and what the context or preliminary concepts are to understanding the explanation.```
(Strictly speaking, quadratics are not functions. Quadratic functions are obtained when one applies the evaluation map to the quadratic. This side note is emphasized when working with polynomial rings.)
I'm not sure what you mean by "removing" an operation. It seems that it could be that you are plotting it incrementally from an easier case to transform it to the general case.
thinking:```
I'm also not sure why you need to talk in terms of code blocks.
The extra syntax highlighting may be distracting.
I don't talk that way all the time, and it's because it looks more professional.
Alright, I may remove the "Lua" modifier as to remove the syntax.
1. Would you be willing to further explain what an evaluation map is along with what polynomial rings are?
2. By function I just meant that the behavior of quadratics appears to work in that you give inputs and receive outputs and the goal is to achieve a result of zero to graph the behavior of it (parabola).```
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