#help-27
1 messages · Page 406 of 1
What does it mean?
Like the < doesn't make sense and how would I mark the graph out like what
numbers
would go for what ticks
Could you show the whole exercise?
Part b btw
it would just mean drawing the whole graph within those sections, if it had < instead it would mean to draw it up to 60 but not on 60 and same for the 0 side of itt
sorry if the wording is weirdd
Ok um
could u explain it based on this (this was the answer booklet)
how was I supposed to know
that those random inequatiles
Random?
would lead to this? and hwo would I calculate the ticks and numbers per blah blah
sorry?
You are given the bounds
oh as in
Why random?
yeh the bounds
You're overthinking a lot
just as filler words inbetween i thinkk
0 ⩽ t ⩽ 60
Yeah
and how do I get to the graph from that generally?
Huh? You're saying that writing 0 ≤ t ≤ 60 is strange? 😱
Well, it depends on the exercise 😅
I dont get itt mann 😭 but my main question is
yeh no nm
ur right i am overthinking it
k thanksss
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Im struggling with understanding the integration bounds, how exactly are they determined
hello you must use the jacobian
No but how should I think about this visually
Like what would you say it means. I made the misconception of thinking I need to find the area bounded by the paraboloid/ellipsoid
@dawn perch Has your question been resolved?
If you want to find the volume of K you would do ∭_K 1 dV
I don't think there's a super clear interpretation of what this integral "means"
Maybe you can think of it as computing the mass of an ellipsoid where the object's density at a point is given by the square of it's distance to the z axis
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weird thoughts
lets consider this proof for √2 being irrational
lets assume the contrary such that p/q =√2
then p²=2q²
so q²|p²
p,q in Z, and gcd(p,q)=1 too htw
yes
so then this contradicts
gcd(p,q)=1 so gcd(p²,q²)=1 cuz no extra prime factors introduced, but q²|p² so gcd(p²,q²)≠1 unless and if q=1
let me get this straight
you just weakened your proof here
lets say q≠1 initially, its not hard to show √2 cant be an integer
until here is already where it contradicts
well theres nothing wrong with it
im not saying it's wrong, im just saying that you are weakening it
andd, how so
look, $\gcd(p^2, q^2) = 1$ and $p^2 = 2q^2$
1 divided by 0 equals Infinity
that already contradicts
and if you're saying like this, then it would still leave a case of $q = 1$ for you to handle
1 divided by 0 equals Infinity
or even $q = -1$ with your condition
1 divided by 0 equals Infinity
it certainlt isnt hard to show √2 isnt an integer so p≠√2 in that case where q=1, which i already mentioned
alright
okay okay
anyways
what's your question about?
you're only saying on how you proved that $\sqrt{2}$ is not a rational number
1 divided by 0 equals Infinity
crosschecking on the proof
i think it's fine here
it's not wrong too
and by using the method you used, you can actually prove that $\sqrt{k}$ is not a rational number if $k$ is not a square number
1 divided by 0 equals Infinity
q²|p² does works nicely on these i noticed just now, lets say we wanna show forall a nth root of a is either
was js saying that
lets try on 4,
4=p/q
$\frac{p}{q} = \sqrt{4}$
1 divided by 0 equals Infinity
p=4q, q|p but their gcd is 1, do q=1 is forced, so p=4, and by initial assump p is an integer
$\frac{p^2}{q^2} = 4$
yeah
1 divided by 0 equals Infinity
works nicely
$p^2 = 4q^2 = (2q)^2$
1 divided by 0 equals Infinity
i was talking about 4 not √4, but what ever , works
would like to hear from other too if anyone's interested
What's your question?
he wanted to check his proof of proving $\sqrt{2}$ is irrational
1 divided by 0 equals Infinity
and wanted to expand on that
eh
just implying q²|p² looks just too good to be true even to me mysef so😭 well a bit more analysis and it was perfectly fine
But if you prove √2 can't be an integer a different way it's fine
whats the actual doubt??
with this its quite easy to expand to various root irrationality proof so, like nth root of a is always an integer or irrational
js proof checking
It's quite easy already with the original proof
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Ig it shows whenever a root of an integer is rational, it's an integer
yup
Which is interesting. This can probably be applied to rings (at least UFDs)
i was doing that exact problem when this came up,
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c?
what happened to the x in 400x and why did you approximate
because its trivial
its also trivial to notice that you dont get the right answer
i dont think its because of the approximation
also, what x are you talkig about?
it cancels out
anyway, as you said, the approximation is not really the problem
if you have something that is 5000 times x, what percent of x is that?
yes
you subtract the initial amount
if something is 8 times the amount of something else, it would be the initial amount plus 7 more
i.e. y=800% of x, or y=x+(700% of x more)
so y is 700% greater
ok hold on, i interpet what you are saying as: 8 compared to 1 ... is 800% of 1
and when it comes to "a factor of"
that should be +1 ?
what
is it just me or
10,000 percent of 500 percent of 20 percent less than x
does this have like, a shit-ton of ambiguity
its a linguistic mess
heyo
no, you need to subtract 100%
oh i was reffering to my solution sheet
so in your case : 500,000 -100% ?
in your case, yes
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can anyone please help me understand why one changes to cubed and the other doesnt? im so confused 🥲
@narrow isle Has your question been resolved?
<@&286206848099549185>
Decision 🥀
its a purgatory…
YOO yes pleasee
basically i understand the formula
yeahh
u multiply the time by the order
time?
but in the first question it says its a squared order
ye
sry can i just ask which question you are referringto
ok
this one
so like the dijkstras one
yep
ok wait ive used dijkstras like once i think 😭
lmaoo dw is calm
so like i neef the nodes and graph tho to solve
the question is unrelated to the order but i can pull it up
ok
onee sec
ok
okeee
lowkey i kinda forgot how to apply dude 😭 ✌️
i learned this once from my friend. If i can relearn i can dm ifyw
idk if thats weird or anythin
its up to u
i mean it looks like abcehj is the right answer, but idk the proof for it
like maybe just find the smallest numbers and stuf bro
:so
😭 ok
mb mb lemme circle
order, i see
for this one its cubed but the squestion says squared
but it’s apparently not correct
yeah but for the 1st picture T = that so like calculating time idk
it says n(n^2)
idk
yeahh thats what i dont get
dawg what class is this for
if its done that for the first question it should do for second
mock tmr
ok sry but still this is like cs stuff tho im bus at that 💀 💀
yea i cant really help i just thought it was n(n^2) lowkey
idk bro
gl i guess ggs
hey if its the two of us mayhe that means no one knows and then the papers basically out of 73
thanks gang
js a mock exam
/73
oh i see
hopefully they don't ask about dikstra idk
ggs bro ttyl,hopefully someone smarter than me can help i gtg
thanks for trying gangg cyas
First person I've ever seen doing decision A-Level further
@narrow isle Has your question been resolved?
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yo is anyone up to explain abel summation?
i don't quite understand it
Neither do I
summation by parts 
thats pretty fascinating
probably not what youre talking about though
yes that
yeah apparently it is
you know any finite difference stuff?
so the intuition is just ibp, right
how do you derive it
just that $g_{k+1} - g_k$ is our discrete 'derivative'
jan Niku
hmm okay
similar to how you derive ibp
idk if youve ever done that
you derive ibp from product rule
so how do you derive this
a reverse summation product rule?
i have a feeling if i write $\Delta (f_k g_k) = f_{k+1} \Delta g_k + g_{k+1} \Delta f_k$
jan Niku
it seems not super familiar
but, try starting from here
@sonic kelp so lets say we sum from 0 to idk n
$\sum _{k=0}^n \Delta (f_k g_k) = \sum {k=0}^n f{k+1}\Delta g_k + \sum {k=0}^n g{k+1} \Delta f_k$
jan Niku
we're actually already really, really close to our goal
notice anything about the LHS?
is it just f_k+1 g_k+1 - f_0 g_0?
do you know what $\Delta$ means?\
jan Niku
f_k+1 g_k+1 - f_0 g_0?
yea
because a ton of the terms die
like for example $\sum _{k=0}^2 \Delta (f_kg_k) = f_1g_1 - f_0g_0 + f_2g_1 - f_1g_1 + f_3g_3 - f_2g_2$
jan Niku
yeah so all middle terms get telescoped
so, were basically there
maybe, just want to adjust our indeces a bit
but we have the result now, i think
so, derivation, pretty fast
just like its analogous to IBP the derivation follows more or less the same
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guys i need help with my hw problem
ok
ok gng
$1+1=1+0^+=(1+0)^+=1^+=2$
nadat12
i think bud over complicated it
{∅,{∅}}
no these are peano axioms
There, that's the solution you were looking for
gng just accept peano 😭😭😭
<@&268886789983436800>
are we serious rn
🥀
Nope
That didn't work twin, dw
You should stop trolling though.
Fortunately
lol it has a genuine answer
Doesn't make it a genuine question
.close
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in the sequence 1111011011110110 (4 1s then a 0 then 2 1s then a 0 repeating), is there an index, k, such that all indecies k2^x is always 0. for example, lets way k=5, this would mean that 10, 20, 40, 80, and so on are also 0s
if there are multiple k s, what is its smallest value
so $k2^x\equiv0,5\pmod8$?
nadat12
eventually $k2^x\equiv0\pmod8$, so $k\equiv0\pmod8$ is the only solution
nadat12
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What are going to be your initial and final moment?
Honestly i just want to know the extension is the spring
When the cylinde ris displaced by x
?
Yes
Maybe they mean that the top most point has double the velocity of CM
So displacement is also double
Ye but im not sure if displacement
Also u can just say double
Im not quite sure
Is small displacement so we can take such assumptions
Then does that mean
If the spring qas say attached
To the bottom
Instead of top
If u displace the cylinder by x
There wont be any extension in it ??
I guess
I would suggest that you ask your teacher
Well because the bottom most point has zero velocity, it won't move
So no extension
However only valid for very small displacement
As in the next instant it will no longer be the bottom most point

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✅ Original question: #help-27 message
When the spring is attached to the bottom of the cylinded, the displacement will be 0 as long as the displacement x is less than the diameter of the cylinder
The spring will only move vertically and not horizontally wrt the incline
The vertical displacement can be neglected
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Can you construct quadrilateral ABCD?
can you show your construction
So how do you find the area of ABCD here?
use this
Well
Danggg
I’m using that
I saw the arcs there
Is ABCD cyclic?
Idk
Well, check if ABCD is cyclic then
Construct BD and measure CAD and DCB
Dang it
Dcb 83
It isn’t cyclic
Man
This question has been haunting me since 2 weeks
<@&286206848099549185>
Yes?
How to draw that fig
Show your work, and if possible, explain where you are stuck.
I did
.
I couldn’t draw the triangle
@tulip kettle
<@&286206848099549185>
Nevermind
draw a triangle
first find area
okkk
👍
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base of tri.ABC???
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that paper looks like it survived world wwar 2
You don't have a question you need to ask, do you? 
Ig not
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Is this the correct fraction decomposition for the above fraction?
split it up
what do you mean?
looks good since the two quadratic factors are irreducible
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Would someone please be able to help explain what the domain and range of a function is?? I am so lost - I feel like I missed a day somewhere they taught it.
im googling stuff but i really don't understand it
send some questions
sure
okay so i understand kinda that basically the domain is just numbers that it can be to not be undefined/imaginary
so like for c x couldn't be 0 because then the denominator would be 0, right?
but like i don't actually understand what the domain is or what it represents
Is this your first time dealing with the domain of a function or do you have experience with basic stuff like finding the domain of a linear or quadratic function?
If I do have experience, I don't remember it
Oh wait is domain just all the acceptable x-values?
And range is the acceptable y-values?
Ohhh mygod
okay i was freaking out
Thanks guys..........
oh im so sorry
as long as you got it
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Could someone help me with this question?
I'm a bit lost - can you add 4e^2x and 8e^x?
No u cannot
I'd say you divide the entire equation by 4 first and then you get a quadratic equation.
a=e^x
when adding or subtracting, only terms with identical bases and exponents are considered like terms, for future reference.
@hexed holly Has your question been resolved?
ahh okay
thanks guys
.close
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hi can anyone help me
!da2a, but.if it's that same question again I'll disengage again
Asking the actual question right away is more likely to get responses.
Asking "Can I ask...?" or "Does anyone know about...?" doesn't give people enough information to decide whether they can help, and answering can feel like a promise to help with the actual question, which they might find themselves unable to.
and cos xVsinx?
yeah
can you post the original without the OCR?
can you disable translation and send another screenshot?
it will be in the ukrainian
That's fine
that looks like russian to me
ok so $f(x) = \cos(x) \sqrt{\sin(x)}$ is your function
Ann
i don't think so.
do you know how to find the min or max value of a function on an interval in general?
test the function's value at all critical points inside the interval and at the endpoints
and
?The largest resulting value is the maximum, and the smallest is the minimum. ?
ok and do you know how to find critical points?
f'(x)=0?
yeah. ok, and can you find the derivative of cos(x) sqrt(sin(x))?
can you find f'(x) or not
maybe no
btw we can continue in russian if that is more convenient for you. unfortunately i do not speak ukrainian
for your reference though, f'(x) is called "the derivative of f" in english
anyway... ok i guess let's try to figure out what you're missing
do you know how to find $(g \circ h)'$ if both $g'$ and $h'$ are known (and exist, obviously)?
(composition rule, or chain rule)
Ann
@cinder minnow
wait did op just fucking leave
yup OP fucking left
.close OP left
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oh what
i have no idea
well, i have one idea but it's a huge stretch. maybe he was a russophobe?
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function y=-x^2+8x-5 is defined in [0,9]
find biggest and smallest value of the function
what have you tried?
-# Okay time to learn how to be a proepr helper from this
Don't mind me 🙏
I actually don't know where to start
interesting, well I can set you on a little bit of an ad hoc with you memorizing the steps
orrrrr we could discuss why the steps work beforehand
yeah that would be awesome
amazing
that would probably be too complicated
oh you meant-
not really! its just simple observation
alr then why not
alright
let me draw something
very ugly function but it will do
by eyeing this graph, can you tell me where the minima(s) and maxima(s) appear?
oh no, i just wanna make sure you know what a maxima and minima look like in the graph itself
ok perfect then
before continuing
are we finding local minimums/maximums or absolute ones?
we're gonna go over both concepts anyways, i just need to make sure of something before we go on
local and absolutes
i think
great alright
do you know how local maximas/minimas look like?
let me graph another thing
ill ask you to
simply point out where they occur with a red dot or an arrow
yeah
can you point them out here?
perfect!
observe something about each and every one of those black dots
something that is very special about them is, if you were to draw a straight line that is tangent to these points
do you notice something?
and here
this black point
is also a local maxima for the previous function
anything special about it?
I have no idea
hm thats okay
I can try to make things quick
what ive been trying to show you is a consistant pattern that all local/absolute minimas and maximas follow
which is, they're always critical points
ohhh yeah
yeah! a critical point for a function is a point where...
the derivative of the function is 0 or undefined or doesnt exist
I see
the derivative is 0 is equivalent to what you mentioned here.
the derivative is undefined if the line tangent to that point is vertical
or parallel to the y axis
like here
so the maxima is always a critical point
indeed. both maximas and minimas whether absolute or local are always critical points
so if we wanted to find maximas and minimas for a function
we have to inspect and search for critical points first
again, a critical point for a function is a point wher
the derivate of the function is 0 or undefined
or doesnt exist but that really only happens with piecewise functions. if you know what that is
I don't
but here's the thing, both maximas and minimas are critical points so even if you found all the critical points for a function, you wouldn't really be able to immediately tell which one is a minima and which one is a maxima
you need to compare their y
well,
these two points are both maximas and its not because their y is positive or where they are relative to eachother
this is how we find ABSOLUTE minimas and maximas
with them having tio have the biggest/smallest y in the function
but for local maximas and minimas, they dont really need to follow that criteria
to get to the point, the way you would identify a point like a maxima is observe the function's behavior around it
-# Mohammad Ali and John Cena example 🤣🤣🤣
as i said, these two points are local maximas
the function behaves in a very specific manner before and after each one of them
deritives positive before
negative after
PERFECT
and what about local minimas?
and you're done!
so to sum what we're gonna do
first, all minimas and maximas are critical points and thus we first find critical points
second, we observe the sinage of the derivative before and after the point to figure out whether its a maxima or a minima
our function is
-x^2+8x-5
not quite
indeed
alright so now that we have the derivative
a critical point is where the derivative is equal to 0 or undefined or doesn't exist (which is a thing for piecewise functions)
yeah
mhm
so we need to compare to 0
indeed
i think we need to check the 0 one and the 9 one
like it says its defined in [0, 9]
so the point where its x=9 and x=0
oh i was gonna explain that after a bit but
well- yeah
so
x=0 , x=9 and x=4 are your supposed critical points
yeah
now here's the thing, because the function doesnt exist before x=0 and the function doesnt exist after x=9 you dont really have to check the derivative sign around them
so now, check the sign between x=0 and x=4
and then the sign between x=4 and x=9
i do that using a table
no
well lets think about it
x=0
before: +
after: +
x = 4
before: +
after: -
x=9:
before: -
after: -
what makes a point critical?
the deritives is 0
hmmm the way you tested the sign does tackle a very important question
that wasnt the only thing that would make a point critical
i put the x in the deritive
I know I'm just gonna explain in a bit
lets get over with why x=0 and x=9 are considered critical points as well..
doesnt exist
indeed!
if you remember
at the start of calculuys
when you were learning about continuity
and derivatives with limits
one of hte main criterias for a derivative to exist at a certain point
was for the + limit to be equal to the - limit
wdym
i think i got the idea
We were taught defining a point to be differentiable by considering moving slopes
From both sides
well that's essentially the same thing!
I see
my wording mightve been a bit off here so exucse me
well for a point like x=0
if you try to calculate the left limit
you'd be surpised to find out that
the function doesnt exist before x=0
and thus the function cannot be differentiated at x=0
Yeah
even tho this is correct, i still got stuff to say about it
first, the function doesnt exist before x=0 and after x=9
you didnt have to check the sign.
oh yeah
before 0 and after 9
and for x=4
it seems like you tested before and after twice?
or
wait no
you didnt
im so blind
so for x=4, what type of critical point is it?
before it was + and after it was -
that makes x=4 a?
max
local maxima
ohhhh yeahhh
that's one of your requirments
now we dont really determine "locality" for x=0 and x=9
because again, the function wasnt even doing anything before 0 and after 9
so how are you gonna test the sign before and after
put the x in the deritive function
yes but you determine a max/min by observing the sign ( of the derivative) before and after the point
there is no "before" for 0
and there is no "after" for 9
yeah
alright
now to determine absolute minimas nad absolute maximas
we do what you suggested at the very start
compare between the y's of the three critical points.
the smallest is the absolute minima nad the biggest is het absolute maxima!!!!!
make sure to sub into the original function and not the differentiated version
to check for the y's
yeah yeah for sure
alr i probably have another question like this
so we can do it together
if its alright
this one also has another sub-question in it
explain why the function y=7 cuts the function in 2 points
hm, what do you think we can do about this?
probably sub 7 into the original question
well
this statement can be rephrased into soemthing very useful
we can compare the 2 functions
"show that when y=7, the function has two solutions"
yeah
what 2 functions?
oh yes. you want to find their points of itnersection which is exactly what you get when you solve them!
by the way.... i mightve not been checking your numerical results. im too lazy to grab a calculator.
so i trust in you that you did amazingly well in the previous question 
sub in y=7 for the original function indeed.
ok new question @short hare
@short hare x^3-15x^2+48x-3
[0,11]
Find biggest and smallest value
oh nvm thats actually not a question in the exam prepartions
hold on
let me get another one
@short hare ok a whole new diff one
-3x^4+4x^3+12x^2-32<=0
what the fuck is that
xd
yeah what do you wanna do with this
Im guessing you mean $-3x^4+4x^3+12x^2-32<=0$
you need to prove it
Itsuki
Grrr
yeah
$-3x^4+4x^3+12x^2-32≤0$
Itsuki
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
wait how do u even start this
Hm
(sorry)
Tell me
Prove that it's less than 0?
no
I assume real inputs
you need to prove that
What about it?
Huh?
I don't know it says "prove these:"
and then this function
Ah i see what you mean
Help
I think they want the function f(x) to be proved that it is always ≤0
yeah
If you have to prove that the polynomial is always less than 0, find it's maximum value
If that's less than 0, then you're done
What happened? This chat is occupied, you can open your help channel by looking for available ones
Ok
As for finding it's maximum value, find all the stationary points, determine their nature, and find their y values.
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hello, this is a mirror and a bunch of rays coming from the right. im having trouble understanding why setting the distance traveled for each beam makes them reflect in such an angle that they all hit the same point
what guarantees they will all hit the same point, how is that even possible
its not intuitive or obvious to me, can someone please explain 🙏
is that a parabolic mirror?
yes
im watching this lecture and the guy says that setting these two segments (with the | mark) will ensure they all hit the same point after bouncing off the mirror
but that's what I don't understand
do you know the analytic-geometry defn of a parabola
locus of a point equidistant from a directrix and focus
no I don't know what any of that means
I can't figure it out without having to dig into these things?
i dont think you can, no
ah I see, then I can probably just accept this fact for now
thanks
@hearty nexus Has your question been resolved?
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Unsure how to get x ?
$4 \log x = (\log x)^2$ or $4 \log x = \log (x^2)$
CherryMan
?
so just simplify this?
i did the latter
How do i simplify?
normally I know you can divide both sides by x
but given its a logarithm i am not sure
do you know that a log(x) = log(x^a), and also log a - log b = log(a/b)
that is not familiar to me
well there are some standard log rules
two of which i covered
another similar one is log a + log b = log(ab)
with these rules can you rewrite 2 lg x - 1/2 lg x^2
that would mean 2= 4 according to this?
i thought the question was to simplify 4 lg x - 1/2 lg x^2
not to solve an equality
or is it?
this is correct
so we should use the latter rule then
well tell me what steps you get
(well its 4 lgx - lgx ^2 firstly)
we cant directly use the latter rule
if it was something like lg x - lg x^2 then that would be lg (x/x^2)
but we have a coefficient of 4 multiplied with lg x
using the former rule we can bring that into the lg and then use the latter
yes
well that would be the simplification of the original question
2lg x - 1/2 lg x^2
can you simplify that using the rules
yes
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i cant find how to represent IG and IC in useful ways (geometry problem, less use of coordinates would be nice)
progress (?) i've made
geometry problem
Post a diagram
Conditional diagram
.close
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is this wrong?
wouldnt cancelling out one of the Ys on the left side make it
2y + 7 / 3
nvm
.close
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Can somrone tell me whatsthe right angle to use for this my answer sheet says it should be sin50 but i font get it
then you just need the 20° and 30° that they give you
but if i use sine law dont i need to compare it with gravity x the weight of the sign
are you solving for the horizontal or vertical components of tension?
I have no clue im js solving for tension😭
ok, the law of sines usually helps when you have 2 angles and their two opposing sides. if you know 3, you can solve the remaining
i think it will be much more useful if you draw a free body diagram

she can open another if she does
