#help-38
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@sturdy skiff Has your question been resolved?
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if i have a form of (2x^3)(x+1)/((x+1)^3)^2 what is the order of operations because cutting the bottom factor before and after is different
$$\frac{2x^3 \qty(x + 1)}{\qty(x + 1)^3)^2}$$
King Leo
yes
i assume it would need to be simplified
to (x+1)^6
then it would be (x+1)^5
after cancellation yes
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Double integral of cos(x) in the domain determined by the area between the curves y=x, y=2x and x=1. Solve using both methods (dxdy/dydx) and check the solution is the same. Can't get the same answer tried many times, I don't know what I'm doing wrong
These are the integrals that I did and the answers that I got. I don't have the paperwork right now but it's just solving simple integrals so there are no mistakes there I checked that 100 times.
can you show a picture of the region you are working with? this will make any issues with the bounds more clear
I think I just realized the mistake sorry after an hour
In the dxdy integral I have to split it no?
yes
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All good except you forgot to put -2.5, and instead wrote (0.5, 2.5) for 14b
I see, thanks!
But in general, do I properly understand basic vector stuff?
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✅
well, lets just say you got the scalar multiplication down properly for the most part
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hm
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?
How do I solve the translation?
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@flint mirage Has your question been resolved?
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ik i am being stupid but can someone pls explain how to find theta 😭 😭 😭 i have lost sm braincells doing this i know its easy but i genuinely cant
the question then asks for the exact value of 7sintheta + 3costheta
which i think i can do
i just dk how to find theta
ye i see but how do i work out the lengths of the red sides
<@&286206848099549185>
same as theta
yeah
and using the two sides you know (1.5) (3.5)
so a = 3.5sintheta
b = 1.5costheta
ohhh
i see
so
3.5 sin + 1.5 cos = 2.5
times by 2
i see
okay
thank you <3
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hi i needed help with this
it wants the area of the rectangles
what are those black symbols?
one of them looks sort of like the number 1, the other I have no clue
That's a 2??
its arabic
yeah persian numbers but they say arabic i dunno
Aren't Arabic numerals 0123456789 though
their number is different
huh
Tamil hasn't dsicovered 0 yet
There's a neat book worth a casual read: The History of 0
fake number tbh
Prove some relation about triangles ABE and AFO
oh rip i messed up nvm (deleted my fake sol)
@pastel stone Has your question been resolved?
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solve for the real numbers x>0 and y >0 the system:
2x+3y-8/x=0
2y+3x-14/y=0
no idea how I should approach this
solve both for y and equate them
mb i made a mistake
you can still solve 2y+3x-14/y=0 for y
multiply by y and apply the quadratic formula
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Hey, please can someone help me with this question
After two hours, how far will Gordon have moved?
No clue
And how far will his amigo Brian have moved?
Well, you've been given the speed.
Suppose I'm driving my car at 100 miles an hour because I'm crazy. In an hour, how far do I travel?
100
Correct. So how far have Gordon and Brian moved in two hours, knowing their speed per one hour?
Where's it say that that was there speed after an hour though...?
Yeah but I could be doing 70mph and have been driving for half an hour
So I only done 35 miles
Correct.
Oh....
So how far do you go if you're driving for 2 hours?
Recall that speed = distance/time, if you want to use that. You have the speed and the time
There are a few more things you know.
Yep.
I believe that's right
I haven't computed it, but I trust you as long as you plugged it in right
Just make sure you haven't used radians instead of degrees which is what a lot of people accidentally do
Do I need to square root it?
Ok
Bete Puttigieg 🐢
oh, that's unexpectedly large
A=12.7
If you plugged it in right then yes
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are those two different equations
@twilit olive Has your question been resolved?
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are angle BFC and angle BFD a linear pair with vertex F
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How do I start?
do you know how to find slope when given 2 points
y1-y2 / x1-x2
you know one of your points P
(1) is asking you to plug in x=0.5 into Q to get your 2nd point
So I just keep plugging the numbers in? What about the curve equation
observe that Q is a point on the curve
So is Q x?
Q is a point on the curve and x is the first coordinate of Q
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So how did the 1/2 disappear in the 4th line
im ngl im so confused
What is the original question?
yeah that flew over my head 💀
wouldve never figured that out without your help bahaha
thank you
Arc length formula is 1+f'?
the integral of sqrt(1+(f'(x))²)
I forgot how it works, it's been a while
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yo can someone help me out with 3, 4 & 5? And can you check if my answer for 2d is right?
Yea ik that
Is my answer for 2d right tho?
I'm a bit confused on 3 tho
Brb
I'm back
<@&286206848099549185>
no
What's the right answer?
A & B are right its just the c that's wrong I think
What goes in there?
there are some elements in C that should also be in B
B is all even numbers to 20
and C is all 2 digit numbers
so numbers like 14 should be in both B and C
same for A and C
Ohh ok
I see now
I thought that the numbers in c are supposed to be different from both a & b
thats the complement
i think thats "not A"
so everything that is not inside A
Ok so A complement is everything not inside of a
All even numbers to 20
A and C
Overlap
A or B all of a & b?
A or C complement idk this
What's d and f?
list the elements out if you're confused
e is all odd and double digits
Pls help me with d and f
I don't understand
Also for question 4. The cardinality is n(A) right?
Is that what it means
?
Anyways what's d and f?
ok d is (A union C)'
A or C complement
A = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}
C = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}
So all odd digits and double digits
The complements are the ones that are not in A or C?
2, 4, 6, 8
I'm lost
even numbers that are?
B
no
C is about two digit numbers
if you take the complement of that what do you say
well almost
yea
So I was right?
i mean you listed out the elements
Alr
but you gotta write it in words
True
f)?
A complement and C complement
A is odd, C is 2 digits
So..
Even 1 digit numbers
Same thing as d
yep
Didn't I already list them
My teachers asking for too much
I understand this part
So let's skip it
3 is to describe it in words without listing
Let's do 5
4 is to actually list it
If u have time
yea that's light
do you know what disjoint means?
yep
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How do I solve these?
I think the first two are ordered pairs (x, f(x))
the inverse flips the coordinates
what does this mean?
neon
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Is this right? im not aware of the logrithimitic rule
,tex .log rules
riemann
oh thx
A quicker way to that outcome is using the log(m/n) = log(m) - log(n) property.
ln(1/4) = ln(1) - ln(4) = 0 - ln(4) = ln(4)
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there are two line segments 1 cm apart, 2 cm long
i pick a point randomly on the left one, and i draw a line at a random angle
so I get a segment in between, sometimes
what's the average length
i did this
Find average value of |tan(x)| on [0, pi]
and i did a simulation, 1.17106
Average length of all possible segments, or just the ones that will touch the surrounding lines
@shrewd ridge Has your question been resolved?
i don't understand
i bet the calc solution is wrong
but how
hes asking if we take into account segments that dont connect to the other line > obviously not cause if not the average would be infinite under this problems "rules"
so just the segments that do connect between the two
Just asking, could we base the average length on the average angle?
What does random angle mean? Unif([0,2pi])?
ok i get it
figured a bit, the problem basically reduces to, chose two points at random from a segment with 2 units of length, what is the average difference/distance
based on that you can figure the average angle, and with that, the average length of the segment
yeah, or [0,pi] same thing
ill work with that distance as this average i do not know as "x", cause from that point onwards the problem ends up being pretty easy+
the angle bounds seem wrong
maybe i'm imagining a different angle, though
solution unless im heavily dumb, with x being the average distance between two points on a segment chosen at random of a segment of length 2
starts from 60° and reaches 90° at middlepoint
i dont know statistics, so chatGPT will be my saviour
so total rad·cm divided by total radians
the average length of the segment is 5/3 cm, neat
i think i must have been measuring from a different starting place
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question 6 and 8
im having trouble doing these becaue i missed classes for being sick just wondering if someone can copme and help me understand the prosses to solving them
also questions 11 and 12
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I need some help with functions
So in task 2
It says i need to find the theme(?) Of the function
The zero poinz
Opening of the parabole
Axis od symetry
Extremhm of the function
And the minimum value of the function
Please guys help
I'm assuming you need to identify whether it is a parabola or hyperbola that sort of thing
@trim stratus Has your question been resolved?
Nmv guys i figured it ouz
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Can someone explain why it's e?
you can use euler's formula to see why
Denote * as conjugate
(cos(z))* = cos(z*)
(sin(z))* = sin(z*)
Shouldn't it only affect the imaginary part?
that is imaginary as well because z is a complex number
ok so if z = a + ib
It's cos(a-ib) - sin(a-ib)
which is e^-ai-b
ooh ok I got it
thx
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Was wondering if this is sound reasoning, would appreciate any feedback, or any alternative methods that may be faster. And yes i understand that a step like checking for a difference greater than 1/3 is arbitrary for this question, but it was moreso as a general step for questions in such a style, as it may eliminate multiple options faster than subbing in x values.
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hi
yes but with bigger numbers it becomes harder and harder so is there a way to do it not in your head?
more complex numbers too
uh take the gcd of any two of them and then take the gcd of that and the 3rd number
nah gcd and gcf mean the same thing
greatest common divisor or greatest common factor it doesn't matter
same meaning
ok so i can only find the gcf of any number once
how would i find it again the second time for that gcf?
thats just doing it in the head though im trying to figure out how to do it manually so i can do it with far greater number
so ill give a more complex question
43 172 246
i think i have a method down though
lemme try it and see if i can find the gcf of that
how do you find it quickly
i just try to guess or do in my head
but the same problem also occures here in larger numbers
just divided 246 by 6
i need a method though not the straight answer, it doesent help me to get the answer because i still dont have the method to find the factors of other numbers.
for advanced factoring techniques
one of the methods is finding the GCF
i understood how to find the GCF of 2 numbers with a rather easy method
but 3 or more is problomatic
so it is just a guessing game
how do you do it for 2 numbers
It is easy to find the greatest common factor using the eucliean method. This is the fastest method of working out greatst common factors short of knowing all the factors for every number!
This method works rapidly even for large numbers and utilises the Euclidean algorithm.
To donate to the tecmath channel: https://paypal.me/tecmath?locale...
tested it and it worked
ok so if you have three numbers a, b, c then just do that on a, b and the do it again with whatever u get and c
ok let me pick 3 numbers quickly and try that out for a sec
308 505 702
lemme do 308 and 505 first
didnt work
i think i fucked something up
i dont have the time to redo this cuz i have to go to work
but ill come back to you on this
@surreal spindle Has your question been resolved?
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how do i solve this? do i use euler's method or i have no idea what this problem wants me to do...
First, what’s your tangent line
So the question is basically asking:
For what biggest $x$ value is:
$$\left| \qty(x^2 - 2x + 3) - (2x - 1) \right|<0.5$$
King Leo
Idk what euler’s method is
its just some approximation method
but how do i determine the error if i dont know the correct one...?
i dont get this 😭
The error in the vertical distance between the quadratic and your tangent line
oh so the tangent line and the parbolas distance should be less than 0.5 and we're finding the maximum x that makes the thing <0.5?
and are we using absolute values cause the distance is just distance here no signs needed
The tangent line con be above or below by 0.5
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how do i solve this? (its calculator allowed question)
i dont know how to approach it
,w maclaurin series e^x
sign doesn't match?
Oh wait
@vocal cobalt use this series
what about the sign
and how am i supposed to know that it will be e^x or whatever how do i identify that?
Okay so the sign is the problem
You’re supposed to know that $e^x = \sum_{n = 0}^\infty \frac{x^n}{n!}$
King Leo
This series can be simplified to:
$$\sum_{n = 0}^\infty \frac{(-x)^n}{n!}$$
King Leo
i should have known what e^x looks like its one of the MUST KNOW series 😭
what about the sign though
If the sign has been changed
Then just change the sign
$x$ turned to $-x$. $e^x$ turns into?
King Leo
$$e^{-x} = \sum_{n = 0}^\infty \frac{(-x)^n}{n!}$$
King Leo
You don’t need to do that anymore
You have now found that the series is just e^(-x)
ohh so cause for -x ^ n sometimes its gonna be - and sometimes +?
$$(-1)^n x^n = (-x)^n$$
King Leo
yea it makes sense
So can you solve the problem now?
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I need to find monotonic intervals
purple is original funtion
red is derivitive
I have no idea how do i do it on paper because I can't draw something like this
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Hi, I would need help understanding the proof of Weierstrass theorem
post it
The professor told us to not learn the proof in a rigorous way, just understand the idea of it and how it works
sure post it
,rccw
oh it's upside down, sorry
I understand what we are doing but I don't understand how it proves the theorem
we end up with ${x_M} = \cap I_n$ so, since $I_n \subseteq [a, b]$ we have that ${x_M} \subseteq [a, b] \implies x_M \in [a, b]$
nico.alesi
but for this to work don't we already need to know that there is a maximum in [a, b] before starting?
State the theorem
Let $f: [a, b] \subseteq \mathbb{R} \to \mathbb{R}$ be continuous, then $\exists x_M, x_m \in [a, b] / f(x_m) \le f(x) \le f(x_M) \forall x \in [a, b]$
nico.alesi
basically if the function is continuous in a closed interval then that interval includes a point of maximum and a point of minimum
the part I don't get is the part that says "after splitting the interval, take the half so that max $f$ in $I_0$ = max $f$ in $I_1$"
nico.alesi
so we are actually pretending that there already is a maximum in $I_0$ = [a, b]
nico.alesi
it has to
but is it legal? to prove it pretending there is a maximum (to prove that there is a maximum)
well prior to bolzano's theorem, there is an even stronger theorem well its a fact tbh
consider any function that is continuous over a closed & bounded interval [a,b], that function has a min & max in that interval
yes but I am trying to prove that and I am assuming that what I am proving is correct
isn't it a loophole?
(sorry I'm not so acquainted with proofs, I don't study mathematics)
ok, thank you for your time
So let me recap, you want a proof of this Weierstrass theorem
My advice is to use Bolzano Weierstrass theorem
no no, our professor told us the idea of the bisection proof
this one
and I understood everything, my only perplexity is, can we assume there is a maximum to prove that there is actually one?
isn't it a loophole?
they probably meant sup/inf?
well they kinda assumed f is bounded
yes but it doesn't give existence of max/min
only sup/inf
still
the picture I sent is all I have
how would they know sup would exist in that interval though? OwO
because the function is bounded, as you said
yes we require BW
conti => bound
the sup exists for sure
yes thats what they try to proof
proof?
weierstrass is a consequence of BW
not the opposite
because if we have $f: (a, b) \to \mathbb{R}$ then $f[(a, b)] = (c, d) \subseteq \mathbb{R}$
nico.alesi
this is another theorem we studied
add continuity there and yeah ur good to go
and why would c,d not be infinite
especially since on this version you're considering open intervals
no, boundedness comes from BW
we straight up jumped that
yo bro Idk what to say, this is what my professor told us, I have no idea
then the teacher who didn't talk about bolzano-weierstrass did a mistake not talking about it
the thing is I am studying computer science and artificial intelligence so the role of these topics in my course is marginal
probably they selected the bare minimum
and thus let out some half baked fake proofs to try to appease the math-oriented people in the course
its useful too tbh https://en.wikipedia.org/wiki/Pareto_efficiency
In welfare economics, a Pareto improvement formalizes the idea of an outcome being "better in every possible way". A change is called a Pareto improvement if it leaves at least one person in society better-off without leaving anyone else worse off than they were before. A situation is called Pareto efficient or Pareto optimal if all possible Par...
you didn't get what I meant
i do i do
I can't do anything about it bro ahahaha
well, it is marginal you'd say but it is what it is
if you want to, I can try to give you a better idea of the proof. As easy to understand as possible
I didn't say all of it is marginal, some things are less useful than others, that's why, perhaps, they let out WB theorem Idk
Proofs are useless for me, I'm not studying mathematics or physics, I just need to understand how the theorem works and it's utility, how to apply it, not why it's true
the scope of that it's beyond my course, I mean, I trust the clever person who found that out ahahaha
we could try
well weierstrass theorem is just about the existence of a global min and max of continuous functions on a closed interval
Ik but this half proof he gave us is just making confusion
that's why I think it would've been better not knowing anything about it
well I can try to rectify the confusion in the best way possible
Bolzano-Weierstrass theorem's proof is almost as easy as the proof of your theorem I'm gonna present
just explain it in a simple way, no need to be rigorous
Bolzano Weierstrass tells you that from any bounded sequence
you can extract a convergent subsequence
that's all you need to know if you don't want the proof
ok
so now take a continuous function $f:[a,b]\to \bR$
rafilou is not not born in 2003
we're first gonna show it's bounded, and then we'll show it has a min and a max
ok
ok so first of all, if f isn't bounded
that means there exists inputs such that the output is as big in the positive or in the negatives as I want
right
yes
yes
yes
still makes sense?
yes that's theopposite of the definition of bounded
welp we just created a sequence $(x_n)$ in $[a,b]$ which is bounded
rafilou is not not born in 2003
so we can extract a converging subsequence
name the limit of that subsequence x
it's pretty easy to see that since all x_n are between a and b
didn't understand this
f is defined on [a,b]
yes
so if find some input x_n for all n
the input must be in the domain of f
yes
such that we have this
I picked them that way
yes, why is it bounded tho
the domain of f is [a,b]
a function is bounded when the Image of the domain is bounded
we're not talking about the image of the domain here
the x are INPUTS
so they come from the domain
not its image
yes but that's the definition
and the IMAGE of those x_n
I know
yes but what I'm not getting is why is the sequence bounded, for it to be bounded the image must be bounded
the sequence (x_n) is bounded
because it's a sequence of INPUTS
so it lies inside the DOMAIN
[a,b]
which is bounded
nico.alesi
this?
rafilou is not not born in 2003
no, I thought we were getting all of the inputs
not at all
we're only getting a countable amount of inputs
we just want to pick a single x_n for each n
such that |f(x_n)| > n
ok
ok
ok so the squence is bounded
the sequence {x_n} is bounded
and so by BW
it has a convergent subsequence
we can name the limit of that subsequence x, which is also in [a,b]
mh
so far so good?
yes
yes
so |f(subsequence)| converges to |f(x)|
but at the same time |f(x_n)| keeps growing up to infinity
so it's impossible
and thus f must be bounded
okk
now that we finally have f is bounded
you can either follow the stupid bisection proof, which works now that we did all this
replacing all mentions of max by sup
or
proving it this way:
since f is bounded, call M = sup(f)
ok
create a sequence of x_n such that f(x_n) -> sup(f)
which is possible due to the characterisations of the supremum
{x_n} is once again a bounded sequence, as it's in [a,b]
take a convergent subsequence by bolzano-weierstrass
f(subsequence) -> f(limit) by continuity
but f(subsequence) -> sup(f)
sup(f) = f(limit)
our limit serves as the desired x_M
repeat for the minimum
end proof
why sup becomes a maximum?
because it's reached
sup(f) is in range(f)
as f(limit) = sup(f)
mmmhh
an upper bound that is also an element of that set
yeah I know that
is by definition, the maximum
I'm trying to understaned why it's reached
could we try the other path?
we know that f is bounded and ok
so we know that there is a sup
and we do the bisection of intervals
ok so now that you have those intervals
we're gonna try to create a sequence {x_n}
such that each x_n is in I_n
and f(x_n) gets closer and closer to sup(f)
it's pretty standard
just take x_n in I_n such that f(x_n) > sup(f) - 1/2^n for example
since a_n <= x_n <= b_n
and {a_n}, {b_n} converge to the same limit
{x_n} converges also to that limit by squeeze theorem
call it x
and by squeeze theorem again, f(x_n) -> sup(f)
but f(x_n) -> f(x) by continuity
so once again we have f(x) = sup(f)
I think it'll take some time to understand this, so I'll read it again
thank you for your time tho
@pure fiber Has your question been resolved?
thanks @nova spire I kind of got it, I wouldn't be able to redo it and reexplain it in this way but since we have to know just the idea I will reproduce the main steps in a more detailed way
basically he said max of $f$ to simplify, it was $sup(f)$ instead
nico.alesi
and I kind of understood everything else
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Can someone explain why a circle or any shape with a curve is not a polygon? Aren't circles just shapes with infinite sides.
I dont think infinity is a real number
It isn't but as you add more sides to a polygon it looks more like a rectangle. So wouldn't infinite just describe a circle.
It approqches a circle but never becomes one
But if that's the case then is it that integrals we can find the area the curve with exact accuracy using infinitly small rectangles
yes
I meant how is it that we can do integrals with infinite rectangle
calculus ✨
I understand that calculus uses infinite intervals with rectangles to find the area but how can that be exact but using infinite sides of a polygon not be a circle
this
by definition of the word a polygon just has finitely many sides
its just what the word means
Ok. But Am i right that a circle has infinite sides?
no
Why
a circle has 2 sides. inside and outside
sides are defined as straight edges of actual length
What does actual length mean
in integrals you never have infinitely many rectangles. you always have finitely many and then approach a limit
thats distinct from ever having actually infinitely many rectangles
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If you have a bowl with six apples and you take away four, how many do you have?
?
how many
!noans
The purpose of this server is to help you learn, not to hand out answers. Do not ask someone to give you the answer directly.
Ok just help me solve it
let me think about this one for a minute
aight
You take away four, and leave two in the bowl
So you have four apples
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Cuz I checked the solutions and it says 6
:)
so idk why
lmao
But you dont have the apples in the bowl
Oh i see
Lol
yeah
ohh
cuz you still have the 4 apples you took out
got it
how do i close
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.close
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given $x > 0 ,ln_x \leq x - 1$ and $(x_i){1\leq i \leq n} , M = \frac{1}{n} \sum{i=1}^n x_{i} $
<rajel />
prove that $\frac{1}{n} \sum_{i=1}^n ln_{x_i} \leq ln\left(\frac{1}{n}\sum_{i=1}^n x_i \right)$
<rajel />
i mean i know i can start with the interval given
and would probably end up with
$$\sum_{i=1}^n ln{xi} \leq\left(\sum_{i=1}^n ln_{x_i}-1 \right)$$
AMGM
this inequality is called Jensen inequality
<rajel />
it doesn't have to do with ln(x) <= x-1, or at least it's not directly related to it
oh really
have you studied second derivatives?
yep
but i dont think this inequality is studied in my class
thats why they probably gave us the ln(x) <= x-1
problem is this is bounding ln(x) by some function that doesn't have "ln" in it
well maybe there is a way
but I don't see it at all, and it's not the most obvious
as was suggested, either you know about concave up/concave down functions and you use jensen
or AM-GM
Closed by @boreal shuttle
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what gonna be the variable
well in the exercice they insist to use the inequation given
i'll try that thx
$\frac{1}{n+1} \cdot \sum_{i=1}^{n+1} \ln(x_i) = \frac{n}{n+1} \frac{\sum_{i=1}^n \ln(x_i)}{n} + \frac{\ln(x_{n+1})}{n+1}$
Goëtia
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how do we know angle C is 39.3 degrees?
sine law here
yes but im failing to understand why angle C is 39.3 degrees
,calc asin(sin(25 deg) * 12 / 8) * 180 / pi
this isnt helping me understand why angle C is 39.3 degrees
Result:
39.340476504462
do you know what inverse sine function is?
also called arcsine
oh is it
sinC/8 = sin25/8?
and then thats 8*sin25/8 ?
then you arc sin that to get the angle ?
12 isntead of 8 somewhere
yes this follows from sine law, once you fix 12 instead of 8.
i understand how the sine law works. i dont understand why C is 39.3 degrees.
you are just giving me numbers and formulas. what did this person do to get 39.3 degrees as angle C
yes sine law is a formula
you have to solve for sinC before being table to take arcsine of both sides
if $\sin(C) = z$ then $\arcsin(\sin(C)) = C = \arcsin(z) $
riemann
I got it now. I think I was misunderstanding why we cant use 8 instead of 12, but i kind of get it now intuitively but i cant explain it
I think sin B being equal to both 39.3 and 140.7 caught me off guard as 39.3 is also angle C
.close
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may someone help
Where do you need help?
So from A)?
c please
Its correct
but with bedmas don’t you do division first then multiplying ??
No
how
Depends in the order of how division and multiplication are written
Mult and division take the same precedence
From left to right
So if I leave from the left there is first ×, then I do the multiplication first
$10*5/ 25 = 50 /25 = 2$
Task Bot
In the expressions the powers are calculated first, then multiplications and divisions, then sums and subtractions; Operations with the same priority must be carried out from left to right.
okay i got 31
If there are relatives first, the rounds are resolved, then the squares and finally the staples; In each case the general rule applies.
$15-2^2+5*4=15-4+20=31$
Task Bot