#help-27
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The context behind this problem is that I have to find out when these two derivates are equal on an interval of -1 to 2
Idk if there’s another way I can set this up, but idk how to solve that
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I think it is easy to show that f is injective
Because f is obviously strictly increasing on R+
For surjectivity I have no ide
Maybe you can try to show that the function g(x)=x^3/3+x^2/2+x-c where c is a postitive real constant always has a positive real root x
What would it look like?
Okay I think I have an idea
Let g(x) be that function I defined in the message above
Then g(0) is negative
But g(x) is a monic polynomial, so when x becomes large enough g(x) will become positive
But then it goes from negative to positive, so it must pass throught the x-axis because g(x) is continuous
Therefore it has a positive real root
And the surjectivity is proven
How can we verify if the proof is correct?
I dont know but I see no mistake in my proof
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Need some help.
Trigonometry.
I would sub sin(x-1) with another variable
u?
Sure
No
confused.
okay
Then go
(u+1)(u-3)?
No that's not how sine works
I know I need to find values that satisfy the equation
so x = 0,pi
right?
@gleaming socket
sin(x-1) = 3
add 1 on both sides
sin(x) = 4
Sin is undefined.
I would find two values on the unit circle where sin(x) = 1
well, one value*
so x = pi/2
What is the value?
so x = 3pi/2
Yes
So where did I go wrong with sin(x) = 0?
This is basically arcsin (-1)
sin (x) = -1
x = arcsin (-1)
Now what is
sin (x-1) = -1?
0?
No, you can't just separate x-1 inside the sine function
What do I do?
3pi/2?
... I'm still confused.
Confused with which part?
Can we start from the top?
so (u-3)(u+1)
u = 3
u=-1
sin(x-1) = -1
Do we not add 1 on both sides?
What happens if you add?
But -1 is inside the sine function
So we can't just subtract?
So substituse the -1?
sin (x) = -1
x = 3pi/2
sin (x-1) = -1
x-1 = 3pi/2
Yes
, calc 5pi/2
Result:
7.8539816339745
,calc 2pi
Result:
6.2831853071796
Wait I think it can still exist inside
?
You know sine is periodic right
This trigonometry video tutorial shows you how to solve trigonometric equations using identities with multiple angles, by factoring, and by finding the general solution. This video contains plenty of examples and practice problems.
Access Full-Length Premium Videos: https://www.patreon.com/MathScienceTutor
____________________...
No solution coz 3 is beyond the unit circle
Only works between -1 to 1
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I dont understand the explaination they have
so you agree that sqrt(x²) = |x| ?
since sqrt(x²) = x OR -x
@wooden dawn

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Is this correct
@calm patio Has your question been resolved?
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@calm patio Has your question been resolved?
You're missing a factor of 2 on the first term since the derivative of 2x is 2, but other than that, yes.
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does anyone have a way of remembering that taylor's theorem is squared at the bottom
taylor's remainder theorem for multivariable calculus
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Closed by @normal vale
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in that case can I just pick x instead of -x ?
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Why is the answer D?
If they're both a "rate at which water __ a tank" then they're basically derivatives. Meaning, we'd choose C to see the total rate of change if it's decreasing?
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f(x) = 2x - 4 and g(x) = 3x + 1
f(g(2)) = ?
I dont really understand how to solve f(g(2))
Do you know how to do f(g(x))
I have nationals tmrw and I'm doing old nationals to study
Not really
I got an answer
But idk if its right or wrong
I got it to 14
what’s the value of x in f(x) when g(x) is the input?
?
f(g(x))^
what is x equal to in f(x) when you’re using g(x) as the input i.e. f(g(x))
Idk
That is
Like
You calculate that by checking what the y value is
When x is 2
Right?
Or am I tripping
no need to draw anything
at all
substitute x=2 in g(x)
g(x) is 3x+1
so sub in x=2 into 3x+1
what do you get
yes
Ye
now put 7 into f(x)
and you are done
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determine the value of a so that the inequality 2x - a < 5 has the solution x < 7
!show
Show your work, and if possible, explain where you are stuck.
I mean
Sure
But its not in english
And i dint really
Hace any work
I just tried calculating it in my head
how did you get 4.5
Uhhhhhhh
I dont remember
Tbh
I dont know how to solve it
So
Could you help me solve it or?
umm ok so lets start fresh
Yea
,rccw
Couldn't find an attached image in the last 10 messages.
nvm
determine the value of a so that the inequality 2x - a < 5 has the solution x < 7
?
consider
2x -a < 5
transpose the stuff which is in lhs to rhs except x
make sure to change the inequality if you multiple with a negative number
right hand side and left hand side respectively
?
How do I transpose it
Yea
what do you get
huh?
no?
Wdym
consider
2x -a < 5
ADD a on both sides
Oh.
it kinda looks like you multiplied by a but you didnt
i mentioned add ' a 'on both sides
BRO?
2x <5+a
look at this
Is it not x <2.5+a
look at this
Is it not x <2.5+a
no
its x< (5+a)/2
bro 4.5 is a/2
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Hello!
I am unsure on how to start or complete this assignment. Any help is appreciated!
Below you can see the photos of the information needed to complete the assignment ⬇️
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It telescopes
Idk how to give a hint, an easy to prove identity kills this
Try to rewrite arctan(1/(r^2+r+1)) as the sum of two arctangents
@restive river Has your question been resolved?
idk how to
@restive river Has your question been resolved?
@restive river Has your question been resolved?
Answer is pi/4
yeah
but
i see lemme check
the answer is 1
@lime walrus
ig you missed one tan
:/
Tan of pi/4
Yup I missed one tan
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hi, just wanted to confirm something for stats -- so ik that mean and standard deviation are denoted differently based on whether its a sample or a population ( x̄ vs μ). is population mean always theoretical?
or no
if you have a huge population, for ex every woman on earth, you could never get everyone so youd have to take a sample
but what about for small populations, like the number of students in one class
The key idea is that statistical methods provide a framework for drawing conclusions about a population based on a subset of data (sample), even if the entire population is accessible. This helps generalize whatever you find beyond the specific group you are observinf
if it's purely about that one class then the population mean can be experimentally determined. even for large populations, that's what a census does (it just gets impractical for larger and larger populations)
right
yeah
idk my teacher put in the notes that μ is the theoretical mean
but statistics isn't really needed if you have a population mean. the point of statistics is mainly to approximate information about a population without actually going through the effort of making a census every time
a sample is taking a small subset of the population whereas a census is surveying everyone
so this is incorrect/?
depends on context. if your're doing a z-test comparing some statistic to a known parameter than it can make sense to call it theoretical
could you give an example?
say you have a new drug, which treats a disease that normally takes 8 days to recover from. we want to advertise that it takes less than that, so we give it to a bunch of patients and see what their average recovery time is. so far, the only people who've taken our drug are the people in our trial. but our measured mean is still a statistic compared to the hypothetical population mean, which would be obtained by giving the drug to literally everyone in the world who's sick, so the population mean only theoretically exists, but it's still useful to do statistics to estimate it (after all, we don't want this trial to be a fluke)
right
i see
alright i get it, thank you so much for your help!
have a great day/night 
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someone help me solve 25
What about it
how do we start
Ah
Product rule
Take the first function as 3x and second as (2x+1)³
${(\frac{d}{dx} 3x {{(2x+1)}^3} )}= {{(\frac{d}{dx}} 3x)}}{(2x+1)^3} + {(\frac{d}{dx} {(2x+1)^3)}} 3x$
bro w lowkey
I forgot the brackets one sec
Lorentz
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It's fine now
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How do you solve this
i tried taking the limit inside and solve the denominator
Which gave me e²
forming again 1^(infinity)
oh wait i should take log
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is the graph drawn correct
And i am not sure how to do c
ohhh okkay rhanks
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Can someone please tell me what the J here refers to? i cant understand it the way the book tells me, and when we did this in lectures, we didnt talk about this j at all.
@drifting yarrow Has your question been resolved?
well the j doesnt seem to appear anywhere else
so it doesnt seem like it matters at all
ah wait maybe just for each dimension?
I mean we can only guess here, there are quite a few notations for which we dont know what they mean in your course. most notably of course P_j. also V(E; G_m)
i talked with one of my classmates about this too, and he suggested the same, i just feel like its such a weird choise of notation, But it could make perfect sense. P_J stands for partition, and the V(E,G_m) is the volume of my set calculated given a certain grid.
well what does the index in the P_j mean
do you maybe have an image of the definition?
Yes this was what i read and couldent understand.
ok
you have the square [0,1] x [0,1]
in both dimensions you split the interval [0,1] into pieces by cutting at the points k/2^m
so for m=1 you have the pieces [0,1/2] and [1/2,0]
for m=2 you have [0,1/4], [1/4,2/4], [2/4, 3/4] and [3/4, 1]
and so on
yes.
and then you just make that into a grid in the cartesian product [0,1] x [0,1]
yes, i get that. But what does j mean? if i were to delete j from the problem i could solve it with just k and m, but j is there, and idk what to say if somebody asked me why i ignore it.
well alright then thanks.
you could for example not split up both axes the same way
then P_1 would be {0,1/3,2/3,1} and P_2 would be {0,1/4, 2/4, 3/4, 1}
..
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I need help understanding how to prove the pythagorean identity
You just plug in 5pi/3 into both trig functions
alright ill try that, Thanks
@sturdy linden Has your question been resolved?
Im having trouble getting past the equation part now
It would become sin^2(5pi) + cos^2(5pi) =1 correct?
then sin^2(5pi/3) + cos^2(5pi/3)=1 ?
Yes
Is that it?
Help how
You have it correct here
How do I evaluate it tho
Ive learn not much about it
Well how you evaluate them depends what you've been taught
Go look in your notes for special angles that you know sine and cosine of
Oh ok I got it
Thanks for your help
When bringing down sin^2(5pi/3) it becomes 3/4 and with cos^2(5pi/3) it becomes 1/4 which =1
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hi
how to find the limit of : 1/x power 3
i am supposed to say that the denominator cant be = 0 but its power 3
how to cancel it or smth
Limit as x approaches what
x^3=0 is when x=0. or what do you mean
as x -> 0?
To find: $$\lim_{{x \to 0}} \frac{1}{{x^3}}$$ ( which I assume to be what you meant) you would have to find $$\lim_{{x \to 0^+}} \frac{1}{{x^3}}$$ and $$\lim_{{x \to 0^-}} \frac{1}{{x^3}}$$ and see if they approach the same value. In this case, $$\lim_{{x \to 0^+}} \frac{1}{{x^3}} = \infty$$ and $$\lim_{{x \to 0^}} \frac{1}{{x^3}} = -\infty$$. Thus, the limit does not exist. The domain is as follows: $$(-\infty, 0) \cup (0, \infty)$$
why latex no work
you have to use $$ around equations
ohhhh. thanks!
Quacker
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is that what your question was or?
you needed the domain too or?
but uh how did we know that 0 is a domain
yea
0 is not a domain, its not in the domain
The interval notation states that 0 is not part of the domain because it is open brackets
Everything except 0
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Hi, more dumb questions 😭 but how do i realize that the sum of all the curved perimeter is the circumference of one circle
These things
Like how would i know purple = 78 degrees
i avoid geometry like the plague sorry
If you follow the line around the circles you make a full rotation and since those curved parts are the only times you change direction and they're all the same they must each be changing direction by 360/5 degrees
geometry sucks! np i think i remember the result from somewhere but not sure how i would’ve done it without that
hmmm nice i think i see
is there a more formal way of showing this?
I would argue that's formal enough
ahaha okay thanks
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Can someone tell me why my answer is wrong?
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An infinite arithmetic sequence $a + b + 4 ...$, and a infite geometric sequence $a + 4 + b ...$, where $a \neq b$. Find a and b.
Good
I can't seem to find a way to combine the sequences.
are you sure that's full statement?
That's all.
so we just have that a_1 = a+b+4 and b_1 = a+4+b?..
a1 = a, a2 = b, a3=4. And a1=a, a2=4, a3 = b.
a bit different from what you wrote at first, but it's fine
My bad, it should be "series".
so, you know that $a_{n}=\frac{a_{n-1}+a_{n+1}}{2}$ and $b_{n}^{2} = b_{n-1}b_{n+1}$?
Alisia
Neither of them have I seen before.
if we assume that a_n if arithmetic progression and b_n is geometric, that's true
so, using that, you can get system of 2 equations with 2 variables
Is there a way beside using those formulas?
yes, since these formulas were derived from the definition of arithmetic and geometric progressions, you can use definition
Is there a provement to it?
$a_{n-1} = a_{n} - d, a_{n+1}=a_{n} + d, b_{n-1}=\frac{b_{n}}{q}, b_{n+1}=qb_{n}$ that must be enough
Alisia
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Joanna Angel
and
$\lim_{x \to -\infty }\frac{-1-x^{2}}{x}=\lim_{x \to -\infty }\left( -\frac{1}{x}-x \right)=+\infty$
Joanna Angel
Joanna Angel
joanna
something which i always wondered was
can you like invert the terms given in the question
and then change the limit to +oo ?
like just reverse the variablea affected by the limits
yes i may write it here too, mmoent
thanks, i will experiment myself
dw dw
at the end of your limit, you should write: +∞(-∞)(0-1) = + ∞
this limit :
$\lim_{x \to \infty }e^{x}\left( x-\frac{1}{x} \right)$
Joanna Angel
hm
such one you meant?
yes yes
like
there are some questions
which i would rather convert in positive oo format
wait let me grab an exmaple
$\lim_{x \to \infty }e^{x}=+\infty\\\lim_{x \to -\infty }e^{x}=0$
Joanna Angel
Joanna Angel
yvw 🙂
let me write generlaly method for limits with cosx when x ->0
wouldnt i just create x^2 in denominator and then = 1/2
$\lim_{x \to 0} \frac{1-\cos\text{}x}{x^{2}}=\left[ \frac{0}{0} \right]=\lim_{x \to 0} \frac{\left( 1-\cos\text{}x \right)\left( 1+\cos\text{}x \right)}{x^{2}\left( 1+\cos\text{}x \right)}=\\=\lim_{x \to 0} \left[ \frac{\sin^{2}x}{x^{2}}\cdot \frac{1}{1+cosx} \right]=\lim_{x \to 0} \left[ \left( \frac{sinx}{x} \right)^{2}\cdot \frac{1}{1+cosx} \right]=1^{2}\cdot \frac{1}{2}=\frac{1}{2}$
Joanna Angel
this limit above, shows typical apporach, how to cope with such a limit
you're right
well ) it is just a computatinal proof, just a calculation
hey i am still a kid so 😭
smiles 🙂
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there’s a for finding midpoints which is (x1+x2) / 2 , (y1+y2) / 2
Can I can use that formula to find the value of p?
or is there another formula
You don't need that, think of a name for the "distance" from a point to another point.
ohh
[ \sqrt{{(x_2 - x_1)^2 + (y_2 - y_1)^2}} ]
GigaChad
yep
oh ok
okk
did I plug in the numbers right
cuz I usually get myself confused when I put it x2 and x1
its correct
oh yea
ok ty
wait so is it -1 or 7
cuz why is there two answers
25=(p-3)^2 +9
16=(p-3)^2
± 4=p-3
so p= 7 or -1
cuz square of pos or neg no is always pos, so you gotta consider both
ohh ok
3^2 and (-3)^2 is 9, like that
what does ± mean
it generally indicates a choice of exactly two possible values, negative or positive
ohhh
could u help me with another one
yep
ig theres an error in the question, it is not possible without specifying the coordinste, whether its x or y axis
huh
wdym
i mean theres a way, do you kknow the midpoint formula?
doesn't matter
it's just asking for the point
on the axis in general
like any point written as (x,y)
pretty sure its 0,2 then
Given points: $(-2, 1)$ and $(2, 3)$
Midpoint formula:
[ \text{Midpoint} = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right) ]
[
\text{Midpoint} = \left(\frac{-2 + 2}{2}, \frac{1 + 3}{2}\right) = (0, 2)
]
GigaChad
cool, then plug in the values in the formula
pretty much
oh ok
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texas
@real fulcrum Has your question been resolved?
so if we were in R^2 and not R^3, then our setup would basically be this
so the probability that a ray from the origin hits the sphere is the same as the ratio of the red part and the entire length of the circle its on
@real fulcrum Has your question been resolved?
not sure yet, I'm reading through a cople of stackexchange posts
my best guess from how I am understanding the stackexchange posts so far is that the answer should be roughly 1/4 R^2/D^2. which is very far from your experiments. so either your experiments are flawed or my understanding of the posts. probably the latter
well, still quite big from time to time
yeah, not sure. but I have to go. good luck
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im stuck on a probabilistic modelling question
I was doing this past paper and cant seem to find where ive gone wrong. this is the question
this is my solution attempt however i end up reaching u_1 = u_2 which according to the question shouldnt be the case
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how do you do this i have no idea, i forgot how to do implicit
Try differentiating both sides
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Here I am again with the same question ive been asking for what feels like the past week
how did they simplify the cosines like that.
plugging in pi!
how do you get that stupid exponent
$\cos(\pi x)=(-1)^{x}$ for $x$ an integer
I know that
🫎 A Certain User(Moosey) 🫎
so how do you get 2 in the exponent?
and?!
$(-1)(-1)^{n+1}=...$
🫎 A Certain User(Moosey) 🫎
that to me does not explain the 2 in the exponent. maybe im just too tired
,tex .exp rules
🫎 A Certain User(Moosey) 🫎
do you agree with cos(n+pi)=(-1)^(n+1)
cos((n+1)pi)
cos(npi+pi)=(-1)^(n+1)
yes
and i moved the -1 out front, into the (-1) exponent.
product rule...
depends on n
an expression for all n,
0 for even n
makes sense
1 for n=1 mod 4, -1 for n=3 mod 4
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Need some help.
I converted 1 - sin^2(A) to cos^2(A) via algebraic. manip.
so cos^2A + 1 = 2cos(A)
I then subtracted 2cos(A) on both sides to make a trinomial
so cos^2A -2cos + 1 = 0
Factored.
ok that's 90% of the way
Yes, that's not a problem
(x-1)(x-1) = 0 yields x=1 twice, there's no rule against that
Which happens when x =
and x = 0?
Yes !
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✅
holdon @zealous harness I have another question.
we would turn this into 1/sin^2x = 2 right?
do we multi. each side by its recip?
Yes so then you would get sin^2(x) = 1/2
but sin^2x / 1 * 1/sin^2x equals 1, no?
That would do nothing since you would have to multiply the other side by the reciprocal as well
when you have 1/sin^2(x) = 2, take both sides to the -1 power (that is, reciprocate them)
-1 power means you flip the numerator and denominator
(1/2)^-1 = 2/1
2^(-1) = 1/2
ahh
so sin^2(x) = 1/2
sqrt.
sin(x) = sqrt1/2
sin(x) = +/- 1/sqrt2
x = pi/4, 3pi/4, 5pi/4, and 7pi/4
pi/4 + 2pin, 3pi/4 +2pin, 5pi/4 + 2pin, 7pi/4 + 2pin
Right?
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How do I find the nature and type of a conic? In my case, the conic is 3x^2 + 4xy + 3y^2 + 4x - 4y + 1 = 0. I also have to find out how to find the center of the conic and its axes (i hope I translated everything good)
Can anyone help me with some precall hmw?
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@near rapids Has your question been resolved?
I don't need the solution, I just need a bit of guidance with what formulas I should use. I tried searching online but I find different answers everywhere so I'm not sure what applies and what not in my case.
@near rapids in general, if both the x^2 and y^2 are positive, then you probably have an elipse or circle. In you case since there is an xy term, it is an ellipse. If you have two squared terms and one is negative, then you get a hyperbola. If you only have one square term, then you get a parabola
and if B was not an xy term would it have been a circle?
Not necessarily, no xy term means you can complete the square in both, but it becomes a circle in your case ince the coefficients of both x^2 and y^2 are 3, leading to a circle. If different, then you get an ellipse
thanks!
I'm still not exactly sure how the 4xy "stretches" the circle out though. But I believe everything I said above is correct
The cross term is a bit funky
it's always a good bet to try to complete the square
i'm not sure how to go about doing that
maybe it's the language barrier but I don't understand what completing the square means
found this in an youtube video, going by this it would be a circle, right?
also can someone please verify if this is correct?
that looks good
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im honestly just confused how to start my equation at
<@&286206848099549185>
What does 8 more and 3 times means in mathematical numbers and symbols
what kind of triangle is it
Isosceles
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\textbf{Question:} If $A$ is a normal subgroup of $G$ and $B$ is any subgroup of $G$, prove that $AB$ is a subgroup of $G$.
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Hi, can anyone help me with this. I don't know where to start
Try and times the top and bottom of the fraction by the same thing, such that it makes the bottom real
Right because really on the bottom you have 1 - x - iy
no
its $$(1+z)^2/(1-(x^2+2iyx-y^2))$$
Flappie
ah wait
oh i forgot to add the 1
Hector
yes
it doesnt cancel out the i though
no
this is horribly confusing
sorry
also i realised ive made a mistake
we can take 1-z
and fill in z=x+iy
to get 1-x-iy
then what is the conjugate of this
1-x+iy
so we multiply both sides by this
and then we should have gotten rid of the fraction
use .close
.close
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hi please help me understand why 3c is 0.5
@glossy escarp Has your question been resolved?
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Both rolling 5 and 6 have equal probability
yes i understand that but how does it connect 'at least one 5 rolled before 6'
Calculate the probability of the complement event
ohh i get it now, thanks
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the domain of $\log_a(x)$ is $x > 0$
Umbraleviathan
However what you have, $log_9(0.5) = x$ is an expression and has nothing to do with domain per se

