#help-23
1 messages · Page 452 of 1
I had those
I'll even show you
anyways
it's literally
I trust you
Right angle triangle hw
dont care tbh
well review*
LOL
alr
:3
ok so for b
I know A angle is 69.8
and I know my C
so Cos69.9=b/23.6
ye?
Yes
alr
69.8*
you right mb
Yes
A = 30º, cosA = 0.86
A = 30.0º, cosA = 0.866
A = 30.00º, cosA = 0.8660
is this right?
some guy just sent me this
21.1, 8.15*
ye?
Yes
pythag first
a2+b2=c2
12.6173
=3.552083895
oops I mixed up my abc lol
lemme fix
a2=c2-b2
2.371391996
so now I know all my sides how do I find the angle?
<@&286206848099549185>
Use trigonometry
bet
alr grasias
this 1
A=39.80557109 B=50.19442891
Ay yo
ndam
help me wit this 1 X_X
I got
7.810249682
<@&286206848099549185>
<@&286206848099549185>
This 1
how come I got that wrong
it should be 50.2
unless I rounded it wrong?
I did 6/5. tan-1 (1.2)
<@&286206848099549185>
soh cah tOA
hi papa 😄
so
O/A = 6/5
then I did tan-1 (1.2)
which gave me 50.19442891
but it says I'm wrong X_X
Recheck sides
Because it is wrong
Id assume a isnt where you think it is
hmm
oh fr?
dam
Soh cah toa
omfg
I was solving for b X_X
lol
said I got it wrong again
I got 56.4
nvm I got it
39.8
ez
this 1
I did tan-1 (15.1/31.9)
why did I get it wrong?
<@&286206848099549185>
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hello
ok helper
I got a question
I've done part a and b
how do I do part c
<@&286206848099549185>
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help
Can someone please explain this to me
im ery lost
help ;_;
<@&286206848099549185>
ee eim so lost
which one?
@lean otter Has your question been resolved?
@lean otter Has your question been resolved?
someone help me ;:-;-;
- State as many facts as you can about an isosceles triangle LUV with base UV. (lol)
How do we help you with that!? It's just a revision question lol, consult google
or ur textbook
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if i were to draw a triangle would the -3 be the perpendicular side or the hypotenuse
or the height wtv

$\cos \theta$ is negative and $\theta$ in third quadrant
Ansh
what do you think are the signs of sine and tan ?
+ve for tan and -ve for sin
huh
@signal herald If I'm not wrong, the sides should be 2 and 3, the negative sign is just an indication for it not being in the 4th quadrant (cuz cos is +ve in the 4th quadrant)
and yes 3 would be the hypotenuse
height² = hypotenuse² - base² [ pythagoras theorem ]
@signal herald Has your question been resolved?
so i would be solving for the height?
yup
also keep in mind; sin is -ve in 3rd quadrant and tan is +ve, so put the signs before the actual value accordingly
what is ve
negative ( -ve )and positive ( +ve )
^
once you find the height
sin(theta) = opposite/hypotenuse
so 2/(hypothenuse, which you'll find through pythogorean identity)
but it's going to be negative since it's in 3rd quadrant
and similarly find for tan(theta)
sin/cos
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I've got this integral: $$\int_{0}^{1} \int_{0}^{1-x^2} \int_{0}^{1-x} f(x,y,z) dy dz dx$$
Sechmo
I'm trying to reorder the limits of integration
but I got lost trying get $y$ or $z$ to the exterior-most integral
Sechmo
I tried equating z=1-x^2 to get the limits of x in terms of z, I got x=Sqrt(1-z), yet I don't know how I should change y limits
Oh I guess I should'nt change them, but I'd like to know, is there anyway I could leave both y and x limits in terms of z?
it can only be expressed as $$\int_{0}^{1} \int_{0}^{\sqrt{1-z}} \int_{0}^{1-x} f(x,y,z) dydxdz$$ or is there a way $y$ limits could expressed in terms of $z$?
Sechmo
@sage idol Has your question been resolved?
Hmmm actually I'm lost about how could I express the integral in order dxdydz
Maybe splitting the integral somehow
<@&286206848099549185> Help, I offer you a 🍪
You have the numeric values of x and y, just replace them into the expressions and calculate them
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@sage idol Has your question been resolved?
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Does anyone know what this question is actually asking?
Sicherman dice are like ordinary dice, except that they have different numbers of pips on their faces. One has 1,3,4,5,6,8 on its six faces, the other has 1,2,2,3,3,4. A pair is thrown. Find the probabilities of rolling the numbers one through 12 with these two dice. Compare with the usual probabilities
Is this just asking me to find the probability that the two dice sum to 12 when added?
and compare with 2 normal die
it wants you to calculate the probability of getting every number from 1 to 12
like whats the probability of getting 1, of getting 2, of getting 3 etc
but it's not possible since the max face is 8
for numbers greater than 9
unless it means the sum
It means the sum, the main special property of these dice has to do with the distribution of the sum of a pair
ok thanks lol that was a dumb question
Neko
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2nd question: Show that if f is a borel function on R and A $\in B$, that ${x: f(x)\in A}\in B}$. Conclude that if X is a r.v. and f is a borel function, that f(x) is also a r.v.
Neko
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@livid blaze Has your question been resolved?
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I am doing volume of solids for calc 2(disk/washer method) I have these 2 equations bounded by [0,3]. If I rotate it around the y axis my radius function is 3^2-(y^2)^2 however if I rotate it around x=3, my radius function is (3-y^2)^2
Can someone explain why?
I kinda dont understand how you can tell which one is which
well you want to get your radius based off of where your axis of rotation is
so for example
for rotating about x=3
you'd want to use (3-y^2) as your radius
since that's the distance from your axis of rotation to your function
what about rotating across the y axis?
gotta try to visualize the shape
i'm a horrid 3d artist so it's gonna be 2d from me lol
still on the x axis one here
that's if i were to actually revolve it around that axis
the orange line being the radius
I think I understand that one
hmm the y axis one is a little harder to comprehend without someone who can't draw
it's an outside radius - inside radius type deal
let me see if i can find one online
is this incorrect?
it's below
oh
like this lol
so it's got an outer radius and an inner radius
and with washers, formula is (outer radius)^2 - (inner radius)^2
man i need to invest in knowing how to draw
uh where is the midline
that's not the exact graph rotated about the y axis
i found it on google and rotated it via the texit bot
I dont understand where the empty part comes from?
blue stuff is solid
and it's revolved 360 degrees
empty stuff is above the graph
Can I visualize it like this
so I have my area and the blue line is x=3
now if I rotate it
I rotate the x=3 as well
then I have two lines, so I kinda just go I need to apply washers here
would that process work?
that works
i'm not quite sure what that is lol
uh what the volume would look like
what exactly does "would this whole be the blue part" mean
@sharp void Has your question been resolved?
oh is it the empty part?
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Guys i'm trying to solve this question but i can't find solution for this system
and there's no option for no solution
the system does not have a solution
in fact if you add the 2nd and 3rd equation you get 0=-2
@late wagon to solve a system means to find its solution set. and the solution set can be, and in this case is, empty
that's in fact a very good observation
can you explain more ?
is there something in what i said that you don't understand?
or do you understand what i said and want me to keep going with my explanation
keep going with your explanation
consider that cramer's rule and the inverse matrix method only work when your system is known to have a unique solution
which your system is known not to have
gaussian elimination, however, can be applied to any system whatsoever
so it's only gaussian elimination? since det==0 so it can't be cramer's rule , inverse
that... yes, in essence that's it
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is this a typo? because for n>=4, the differential of x^3 is 0
Derivative*
yh my bad
you're right that the >=4th derivative of x^3 is 0 but its not a typo.
wait whaaa
I don't really see how the the >=4th derivative of x^3 being 0 means the nth derivative of x^3lnx couldn't be that so its hard to correct your misunderstanding without you explaining why it would do
oh
wait is the derivative the same after 4
because no new terms are added
thats why they said it
no the derivative isn't always the same after the 4th one, as written it depends on n.
i meant like
you wont be getting any new terms
yh ur right the coefficents change
.clsoe
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I've been trying for hours to work out the answer to this question, and haven't got anywhere
I procrastinated by making a desmos newton method iterator https://www.desmos.com/calculator/lnthuic5n3
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(disk/washer method from calc 2) I am trying to find the volume of the solid generated by the region bounded by y = 3x2
y = 0
x = 3
The axis of rotation is y=27
can someone help me with the equation? I think it is this
I don't understand where this comes from
If you're using disk, then surely you're integrating dy
If you're using shell, then dx
Draw a picture to avoid confusion . . .
Oh wait, you never said what the axis of rotation is. I was assuming y-axis
the axis of rotation is y=27
@sharp void Has your question been resolved?
Uh well the answer sheet said I was correct. Ngl it is kinda jank and I couldn't believe I got it right
yh ok, this seems fine
well you just have to have the correct image on paper
(or in your head)
Just to clear something up, the radius is the distance from the axis of rotation to the curve right?
uh
The center is the axis of rotation
Depends which radius you're talking about
But yes, basically ig
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✅
that's the radius of the hole you marked
yes
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is this a good start or no?
Are you looking for the length of x?
yes
What was your thought process so far?
i thought we had to do a proportion
I don't think that is a good start.
You should apply some statements relating the sidelengths of a triangle with a 90° angle.
what do you mean by that?
Pythagorean theorem
also inverse Pythagorean theorem maybe be helpful if you know it
yeah i haven’t learned about inverse pythagorean theorem before i think
In that case the only solution I am seeing atm is to make a system of equations using the Pythogorean theorem twice and solve for x.
You can apply the Pythogorean theorem both to the left and the right triangle.
do we divide the 12 like 12 divided by 2 to get the two sides?
We don't know the correct fraction so no.
We can only say that the upper left bit has a length of 12 - x.
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They substituted x = a tan y .... my question is how can they change the value of function x to any value?
i mean to say how can we just assign any value to x?What if we put x = a sin y ...will the integral be the same?
Can you explain what you mean
No if we assign x = a sin y
y being the keyboard equivalent to theta in this case
If we do that the dx = a cos y dy
Which is different
They used this substitution that they did because it works out nice
Tan^2 + 1 = sec^2 if im not mistaken
i mean to say, that we have assigned x = a tan y...my question is .... how can we just assign x to anything since x itself is a variable and assuming it's value to be a tan y would make whole function to change
We substitute it in such a way that x doesnt change
X is a variable
And in this case it can be anything because its an indefinite integral
But imagine it wasnt
Imagine x is between 3 and 6
Then we substitute x with tan y in such a way that tan y goes between 3 and 6
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how do u verify this trig identity?
cosec 2θ - cot 2θ = tan θ
i turned cosec 2θ into (1-cos 2θ)/(sin 2θ), and cot 2θ into cos 2θ/sin 2θ....and im stuck there
@jagged cargo Has your question been resolved?
Use double angle formula
now im left with (2sin^2θ)/(2sinθ cosθ)
Do you know how to simplify that?
nope, thats where im stuck
treat sin(t) like its own variable
sin^2(t) = (sin(t))^2
Also cancel the 2 from numerator and denominator
so u cancel both the 2s and the square?
if i do that, then it will be verified, but thats if i do it
right
Look in your algebra book for algebra rules
ah i get it
u seperated the 2 from the sin
???
ok i think i got it
thx🙏 @plucky elk
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I think I'm supposed to find how many ways I can split 5, 6, 7, 8, and 9 into four groups (a, b, c, d) and add them together, but I'm not sure how to use combinatorics/permutations to do that.
let z=a+b+c+d
4<z<10
z=5,6,7,8,9
result=no of ways of picking a,b,c,d such that they sum up to 5+no of ways of picking a,b,c,d such that they sum up to 6.....9
5->1,1,1,2
combinations of taking 4 numbers in four places but 3 repetetion
6->1,1,1,3 or 1,1,2,2
=combinations of taking 4 numbers in four places but with 3 and 2,2 repetetions
find for all numbers from 5...9 and add the total combinations
How would you calculate that without having to count everything, though? D:
its just 5 numbers so do it manually
I feel like that would still take up a lot of time. I'm practicing for a timed test that will be 30 questions in 30 minutes, so I don't think I'd have time to count each one.
i dont think there is a formula for this but maybe try to figure it out and let me know if you find
Ah, okay.
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hey a friend of mine wanted some help with this..
Can somebody explain this to me
@timber valve this dude ;-;
@wet sluice please read the #❓how-to-get-help channel
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how do you do this question without a calculator
$9=3^2$ and $27=3^3$, so the equation can be rewritten as $3^{x+1} = 3^{-3}$. Now take log base 3 of both sides.
OurBelovedBungo
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you have to think of what can go wrong on the top and bottom of the fraction
sqrt() goes wrong when the inside is negative
and the bottom can go wrong if you divide by 0, so you'll have to factor the bottom to find out where that is
@modest cloak Has your question been resolved?
im still lost
there can never be a negative number inside a square root because when you square a number it can’t end up negative
so take what is inside the square root and make a rule that it has to be equal or greater than zero
that’s the first condition
because the function is a fraction, the denominators in fractions can never be zero because you can’t divide by zero
so take whatever is in the denominator and make a second condition that it cannot equal to zero
now you have two conditions, just have to find the common values in those two conditions
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How do we solve this simultaneous equation
A lot of ways
Solve for n or m, ur choice, then substitute into the other, then backsubstitute to the original
The thing is i dont know howw too..
2m+4n = 9
m=4.5-2n
-3m+5n=14
-3(4.5-2n)+5n=14
Solve for n and then u can find m
Any steps that i can follow?
Like in general?
Isolate a variable and then substitute into the other eq
Or set up a 2x2 matrix augmented with the constants and row reducs
Ill try my best tysm
$\begin{bmatrix} x_1 & y_1\ x_2 & y_2 \end{bmatrix}$
MattDog_222
I cant remember how to augment on tex rn but the constants go on the right and then u have a formulaic way
Havent watched the vid but this might help https://www.youtube.com/watch?v=2INfJs5WaFo
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The problem:
Solve the system of equations using a matrix:
x-y =18
x+y= 2
The solution: (10,2)
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An hour
He needs to wait an hour
Uhh
Btw B(x) is 18 I think
But idk
Wait
Nvm
Uhh
I can help you simplify this
This one
Wait
X = (-b+5.5)/0.25b
That’s the answer
X is -b+5.5 divided by 0.25b
Does that answer you wuestion
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@tropic wharf Has your question been resolved?
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hi can anyone help with 4b and 4c? i got the correct answer to 4a but i think my diagram might be missing something?
@alpine crest Has your question been resolved?
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hey everyone
it is to be solved with spherical coordinates
however I think im not substituting it correctly in my denominator which is why it turns ugly
what I get from the region is that my set of bounds is 0-1 for r
0->2pi for phi and 0-pi for theta
but how to I sub my coords in the intergrand?
I see it's an offset sphere
but I dont know how to use that to my advantage
whats the jacobian
r^2 sin theta
that will be multiplied right?
aye
so u get that thing times dr dtheta dphi
yea
uhhh interesting
answer's 2pi/3 btw
verified with wolfie too
-4z ?
What does z become?
-4rcos(theta) would be better
alright so cant u integrate this wrt r first
umm this ?
complete the square under the root?
I mean
theta is just constant
i wont know the difficulties until i try then ig
but im kinda sure this is the way ur meant to
I tried inputting that sort of integral in a caluclator
the result was..
not exactly nice
10 terms with imaginary numbers type of not nice
Is this called multivariable integration?
so it really makes me think there's a nicer sub I could do but im not sure what it is
umm I guess?
goes by triple integral here simply
Ah got you
@crisp lodge Has your question been resolved?
Did you get: $\int_0^{\pi} \int_0^{2\pi} \int_0^1 r^2 \sin^2 \phi \cdot \frac{\dd{r}\dd{\theta}\dd{\phi}}{\sqrt{r^2 \sin^2 \phi + (r\cos \phi - 2)^2}}$
Ansh
hmm?
then? I did the $x^2 + y^2 = r^2 \sin^2 \phi$ thing before writing
r^2sin^2(phi)sin^2(theta)=y^2
Ansh
ohh okay
right
yea
same thing
except it should be theta instead of phi
but that's not that big a deal lol
so yea yea
we're on the same page
wait
its sin(phi) on the numerator, not squared .. ?
the jacobian is r^2sin(theta)
I wrote squared 
$\int_0^{\pi} \int_0^{2\pi} \int_0^1 r^2 \sin \phi \cdot \frac{\dd{r}\dd{\theta}\dd{\phi}}{\sqrt{r^2 \sin^2 \phi + (r\cos \phi - 2)^2}}$
Ansh
Oh right..
yea that's it
Yep.. Is it fine now?
looks fine
that's why I was wondering why it looks so tough lmao
Now it's easy
$= \int_0^{\pi} \int_0^{2\pi} \int_0^1 r^2 \sin \phi \cdot \frac{\dd{r}\dd{\theta}\dd{\phi}}{\sqrt{r^2 -4r\cos \phi +4}}$
-4*
-4rcos(phi)
Ansh
you really are aren't you /bigsarc
aye !
we can first integrate with respect to phi, can't we? 
it's def an option.. I haven't considered that
idk if it's gonna be easier tho
actually no wait that can work
numerator is denominator's derivative
$= \int_0^{\pi} \int_0^{2\pi} \int_0^1 r^2 \sin \phi \cdot \frac{\dd{r}\dd{\theta}\dd{\phi}}{\sqrt{(r-2\cos \phi)^2 + 4\sin^2 \phi}}$
Ansh
we dance around XD
the thing on top is bad :D
What in the world is this
to integrate w.r.t. other variable first?
so far it fits waht I got
u can switch the order of the integrals
Ooo yayyyy
$\int_0^{\pi} \int_0^{2\pi} \int_0^1 r^2 \sin \phi \cdot \frac{\dd{r}\dd{\theta}\dd{\phi}}{\sqrt{r^2 -4r\cos \phi +4}}$
Ansh
wait so now that will be
2r^2/4r (sqrt(-4rcos(phi)+r^2+4))
if we integrate wrt to phi first
does that look right ?
waito
$= 2\pi \int_0^{\pi}\int_0^1 r^2 \sin \phi \cdot \frac{\dd{r}\dd{\phi}}{\sqrt{r^2 -4r\cos \phi +4}}$
Ansh
$= \pi \int_0^1 r \qty[\sqrt{r^2 -4r\cos \phi +4}]_0^{\pi} \dd{r}$
$= \pi \int_0^1 r [(r+2) - (r - 2)] \dd{r}$
$=2\pi$
Ansh
omg u guys did it?
1/3 is missing
Lmfao
.
hmmmmm
r^3/3 👀
which squared term?
the bounds for phi ._.
whaa?
that should be the result after applying bounds
cos(pi)=-1?
lol
Which step?
Is this step right?
the integrand seems fine
Okay so now we apply bounds:
$\qty[\sqrt{r^2 -4r\cos \phi +4}]_0^{\pi} =\sqrt{r^2 +4r +4} - \sqrt{r^2 -4r +4}$
Ansh
No?
careful for sign
=_=
the root of one of those u bodged
and then
r*[sqrt(r^2+4r+4)-(r-2)^2] ?
heheheh
wut
hmm? why squared lmao
both are under roots
wut
(@_@;) what about them.. r belong to (0,1 ) ... ohhhhhhhhhhhhhhhh
SHuri you're genius
Deus this wrong asf smh
Because $\sqrt{r^2 - 4r + 4} = \abs{r - 2} = 2 - r$
Ansh
heheh
i knew it was r^2
$= \pi \int_0^1 r \qty[\sqrt{r^2 -4r\cos \phi +4}]_0^{\pi} \dd{r}$
Ansh
$= \pi \int_0^1 2r^2 \dd{r}$
Ansh
wow nice step
$=\frac{2\pi}{3}$
Ansh
oh right
Yay!! I solved my first triple integral lmao
the second was also a square
help-2 your next integral awaits @final loom
i-
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how would i do this
This is calculus?
dont know
Rewrite (2n + 47)/(n + 1) as 2 + 45/(n + 1) if you're not familiar with limits
how?
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hi can anyone help with 4b and 4c? i got the correct answer to 4a but i think my diagram might be missing something?
@alpine crest Has your question been resolved?
<@&286206848099549185>
@alpine crest Has your question been resolved?
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So I don’t know how to do said problem
2(x+y)squared -9(x+y)+4
is that expression equal to what?
hm
$2(x+y)^ -9(x+y)+4
Sorry I'm afraid I can't help. I thought it was something else
(x+y)^2 = x^2 + 2xy + y^2
wait
I don't know how to simplify this into something actually nice looking
It’s factoring
Have you simplified the (x+y)^2
i got 2x^2 + 4xy + 2y^2 -9x -9y -5
Absolute_5C
Yes 2x^2 + 4xy + 2y^2 -9x -9y -5 was the furthest I was able to simplify
Probably some factoring needed to be done here
WHAT????
i don’t know what kind of problems they be giving me
<@&286206848099549185>
Write u=x+y
And then use quadratic formula for u
Oh there's probably a simpler way
(u + a)(2u+b) = 2u^2+2au+bu +ab
(2a+b) = ? And ab = ?
Solve this system of equations for your constants
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can someone run me thru this question
i forgot how u answer stuff like this with modulus function
all i know is that modulus ( the : | | ) means that everything inside is positive
@lean otter Has your question been resolved?
How are we supposed to help you sketch?
What do you need help with?
It should look like two diagonals from the first and second quadrant approaching wherever a is
If a = 10 the y intercept is 10
And the x intercept should be 2x + 10 = 0 which comes out to -5
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how can i show that the largest area of a square inscribed in an unit cube is 9/8?
Is this for a calculus based class
It might come out to a parabola or something
what if we used analytical geometry?
Wait specify inscribed
by inscribed i mean that all of the 4 corners of the square are contained within or on the unit cube
I guess the maximum would be like
Across the diagonal?
Im still not sure how youd prove that even if that is the case
it is easy to see the area is bigger than 1 and smaller than 2
because the diagonal of a cube's face is sqrt(2), and if the side of the square passes through that diagonal, it will have to go through the height of the cube, wihch is 1, therefore it's not a square
and it's bigger than 1 because that'd be just on the cube's face
Oh thats true
Hmm
Yeah Im not sure the best way
The best way I could think of is brute force
analytical geometry could work, but you'd have 12 variables, no? 3 for each point and there are 4 points
Yeah
and that's too annoying to deal with
I mean maybe you could simplify it to less variables
But theyd likely be harder to deal with variables than position
@lean otter Has your question been resolved?
i'll just drop it, maybe it is too much for me
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im so confused with these, watched couple vids and still lost
how did you get f(a)=4?
ok, well if I asked you for f(3), what would you do?
not sure
.
58
Pretty sure thats correct 👍
yes, and what about f(0)?
4
yes
so, without overthinking it, what's f(a)?
Hint: It won't be a number, cause a isn't a number
tahts the answer for the first one?
f(a)=6a^2+4, yes
2nd question is 6 (a+h)^2 + 4?
check for typos
2nd question is 6 (a+h)^2 + 4?
yes
.close
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If the momentum of a quantum particle is it's mass times its rate of change of average position, why is the momentum of this particle nonzero, it's wave function amplitude is the same at all points
PS, If you answer this question please ping me
#old-network for physics server
I understand this is a physics problem but the physics discord is a lot slower at answering
In griffiths, they say the momentum p=mdx/dt where x is the average position
and then they derive the momentum operator
what step are you lost at in the image
explain it in math terms
This problem can't be solved with just math i think
you should understand the physics involved then ask your question again in math terms
and also look this up if you haven't
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DevFire, ping helpers at least 15 mins after your question was asked
as the rules state
i tried
@crisp lodge
but im not sure
to be honest
i dont know how to make the system in this case
i mean I know that its going to be 60d
d represeting the days
but like i just cant build off of that
maybe, try to define the amount of pages in total of the book
the pages and days come together

