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<@&286206848099549185> Taylor Polynomial. Question: \ Given function: \ $f(x) = \sin(-10x^{2})$ \ Find the Taylor polynomial of f(x) of degree 8 and centered at x0 = 0.
HqppyFeet
What is the taylor series for $\sin(x)$?
Moosey
,tex .maclaurin
HqppyFeet
Yes, and so you know $\sin(x)=\sum_{k=0}^{\infty} (-1)^{k}\frac{x^{2k+1}}{(2k+1)!}$ and since you're asking about a Maclaurin series for $\sin(-10x^{2})$, what would we plug in for $x$ into the Maclaurin series for $\sin(x)$, and what is the maximum degree of that polynomial we want?
Moosey
the maximum degree of polynomial that we want is 8.
and we would plug in -10x^2 into x into the maclaruin series for sin(x)
Mhm. I suppose you could write out just a few of the terms, because you're only looking for an 8th degree polynomial. To be clear, I'd write out the first few terms of $\sin(x)$ Maclaurin series, plug in $(-10x^{2})$ in for them, and get rid of all the terms strictly greater than degree $8$.
Moosey
I mean it lists it on the Maclaurin table too, so just write out those!
:)
then plug in (-10x^2) in for each x
then get rid of all degree terms strictly greater than 8 (if there are any)
so only when k = 0 and 1?
I did spoil myself with looking at the answer, but when plugging into the maclaurin series, the first two terms was the answer...
and I don't fully understand why đ
well what happens to the Taylor polynomial when we try to add $\frac{(-10x^{2})^{5}}{5!}$ (the third term)
Moosey
the polynomial is greater than 8
mhm
but what we found is a polynomial less than 8 
we stop at the first term where it's greater (we do not include it in the Taylor series)
this method does feel weird at first, but I guess I just have to accept it lol
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please help i dont know how to even start
do you know what $\binom{40}{4}$ means
Kaisheng21
its a vector
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The y int would be when x is zero so if you plug that in...
so the coord would be...
(0,-57)
right
I think you have to solve for roots to find the x
wdym plug it in
ok
so the potential rational roots would be plus minus
1, 3, 19, 57
assuming thats correct you can rule out 19 and 57
which theorem thing?
uh
Rational root theorem
rational root theorem
took the factors of 57
1,3,19,57
over factors of 1

ok im just gonna say it's 3
yeah its prob 3
find where both are positive or both are negative so when you divide it both a positive or >0\
does that make sense?
then do the opposite to find when <0
if you know how, a sign chart might be good
so you see the intercepts of f(x)?
basically from -infinity to -7 everything would be positive right? so you would kinda mark a plus there
lemme see if I can find an example
basically you would write out your roots or int
then between and beside them you would write out if it's positive or negative
ah
could you explain that
its basically how you start it
i understand that from neg infinitity to -7 f(x) would be positive
right
why would g(x) be as well tho
like wher eis it
the grpah itself
cuz either neg/neg and pos/pos
for x>0
maybe idk
it wouldn't its just you find the parts of f(x) that are, and then you can kinda visualize where everything is what
for this prob ig you dont really have to do a sign chart
but bascially you see how from neg inf to -7 f(x) is positive and g(x) is negative so k(x) would be negative
yea
just keep doing that with each part to find out the intervals
right so thats not in the interval
oh i thought u said it was
got confused
(-7,-1)U(4,8)
would tha twork, both neg i assume
idk
wait no sorry your right
good
i mean positive 8
yeah thats good
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can anyone explain this to me pls?
the answer is as follows but I'm still confused
do you want the answer explained in detail
or do you want something independent of it (which may or may not resemble it in part or in full)
@mild basin
sorry, was afk
back now
I am open to any suggestions here
explained in detail, or independent if it's easier than the above method
ty @pseudo basin
ok, i've numbered all the steps
can you tell me the earliest one that confuses you
@mild basin
@mild basin Has your question been resolved?
Tyvm, checking it over now
why the half hour delay?
Sorry I got called to eat
What do the || double pipes mean?
||AB||^2
length
aka magnitude
aka norm
whichever of these three words is familiar to you
OK
Is that with or without the ^2?
They all seem to include ^2
It would not be correct if you remove the 4 pipes from AB?
it would become nonsensical
no such thing as the square of a vector
anyway $\nrm{v}$ denotes the length of $v$.
Oh
AnnGhost
Why no such thing as the square of a vector?
Vector is starting point and tail iirc
Like (3,4)
x,y
Just a point on 2d plane
yeah sure and?
Or (3,4,5) point on 3D
dot product exists
if you're talking about squaring each of its coordinates
you can do that
but it doesn't have much meaning geometrically
OK
dot product exists, and one may take the dot product of a vector with itself, but for the love of god don't call it the "square of a vector".
are you asking why they worked out |AC|^2 before |BD|^2?
Well, that too
Would it change the answer?
I would guess yes
Since the question asks for AC + BD and not BD + AC
Are these lengths commutative?
they're NUMBERS, avid.
is addition of real numbers commutative, or is it something that you just now decided might somehow fail to be so?
So it wouldnât matter the order?
Well.. Multiplication of matrices are non commutative
But thatâs different
multiplication of matrices is non-commutative.
yes.
but even for them, addition is commutative still.
Why capital letters?
the capital letters denote points here.
I thought notation is capital for matrices generally
two capital letters concatenated, properly with a little arrow on top, means a vector.
Lowercase for scalars and variables etc
no, capital letters do not always mean matrices.
OK
you have it the wrong way around.
matrix => uppercase letter
uppercase letter â > matrix
OK
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This is my last question of the night (about to attach work) but i cannot figure out how to approach any kind of shadow problem
This is what I was able to figure out myself and I think its correct
I just cannot figure out how to relate everyhting together
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uh I have a question about 3d trig, its a proof question
its just q7...
i cant rly understand why its times instead of 300 over cot blah blah and i dont get why the cots are minused from each other...
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How would you continue the proof from here for this question?
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Donât know where to begin and canât even understand
No
Ah yeah I kinda remember it
So basically 8! Is 8x7x6x5x4x3x2x1
the fraction be shortened due to multiplication
Over 4x3x2x1 power 2
yes
yes albert
so you cna cancel 4x3x2x1 with 8!'s 4x3x2x1
as 4x3x2x1 appears both in the numerator and denominator
then you have another 4x3x2x1 left over
because its (4x3x2x1)^2
and you can see that 8 = 4x2
so you can cancel the 8
Better approach is to square it first.
Wait Iâm sorry, In the denominator, do I power the 4 first?
I wouldn't
I would just write it out
as 4x3x2x1 * 4x3x2x1
and cancel out terms with the top
So basically itâs 8! / (4!) x (4!)
yes
So simplified would be 8x7x6x5 / 4!
ok good luck
Would you be free for another question?
surei ll try my best
I have 2 more questions one is so simple but I got the answer wrong somehow
9 and 10
9 sin should be opp / hyp
Which would be b/c (D) but the correct answer is c somehow
Alright then 10
what did you try for 10?
I think the most common error for a questionl ike 10 is that when expanding, they don't apply the minus sign to all terms in the second polynomial
it should be 6a^3 - 5ac^2 + 12c - 4c - (-3a^3) - (-2ac^2)
and - (-) turns into +
So beginning would be 6a^3 - (-3a^3) which would be 9a^3
correct
and a good observation is that H) is the only option that has 9a^3 so it's the answer but, it's best to solve the whole problem and check
So final answer, 9a^3 - 3ac^2 + 8c
yes
Will that was quite simple
Problem with there ACT questions is it gets my mind twisted, I manage to get the harder ones but get fucked on the simpler one
Thanks man
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I need help setting these up
@frigid brook Has your question been resolved?
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Question: Roll a fair standard 6âsided die until a 6 appears. Given that the first 6 occurs before the first 5, find the expected number of times the die was rolled.
Not sure howw to start it as I thought the die rolls are independent so would just be 6?
oh ok so then is it 5 rolls instead?
it makes sense, like you actually stop if 5 or 6 appears
so 1/3
and then there's no further bias from only caring about half of those
well sorta, i don;t fully get it
hmm yeah ok I think that makes sense
I need to restudy prob and stats.... I have trouble understanding it lol
like you basically are rolling a die and stop when you get a 5 or 6 and then you know you get a 6
yeah so then 1/3 probability then 3 rolls
So I think if the numbbers switched like youre rolling a die untill a 5 appears, given that a 5 appears before a 6 what is the expected number of tosses
thaat should be the same
any 2 numbers on a die then I think
thanks!
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why is this wrong?
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Find the domain, all increasing and decreasing intervals, all local extrema, the intervals of concavity, all points of inflection, end behavior, and sketch a graph.
f(x) = e^2x-4e^x
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Show your work, and if possible, explain where you are stuck.
I am stuck on sketching a graph with the information I have
i think sketching a graph would be the last step
have you found the other pieces?
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!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
Employ the chain rule
I can see the chain rule with the dy/dt part but i dont see what the correlation is between those g(2) g(3) stuff
Some of them wont be needed but some of them you can plug into whatever you get for yâ
is the chain rule for the question df/dg * dg/dt?
You should have a composition in there
write it out using lagrange notation
wait o
im dumb lmao
10 got it thank you @jade oak @hybrid elk
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will i come across a situation where both of the results ( highlighted ) becoming true?
Wdym
That will be contradictory, a can't be < 0 and > 0 simultaneously.
That's what I thought
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How do i draw graphs without having a calculator?
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Not sure what to do here
how to find the derivative of this?
I've tried doing $\frac{1}{x^2+2y^2}\le \frac{1}{x^2+y^2}$ but I can't seem to figure out what to do about the top
clacii
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this channel is already taken but i'll help you anyways
so you want to find $f'(x)$
clacii
clacii
you can then expand and remove the -3 because derivative of a constant = 0
so now we have $\frac{d}{dx}x^2lnx^2$
clacii
clacii
simplifying to give: $2x(lnx^2+1)$
clacii
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Does someone have a good explanation to the rational root theorem ? Having a hard time understanding it
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how do you answer the second part
I got linearly dependent by doing row ops
x3 is free
but idk how to find the scalars it's asking for
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yes
and the solution to it is a dot no?
what does dot mean
why
try it
im not sure wym
conjugate property
what property is it
yes and?
plug that z into here
it flips sign of the imaginary part, by definition, so the real part stays the same.
misleading word use by me ngl
not a property
mb
thats why we have x-x
so real part of z is 0
yeah it obliterates
obliterates lmao
so there's not just one solution
did you do this?
if i do something like
2+yi-2+yi
it still will be 2yi
yeah its that for any real value
so its always just 7/2pi
well yeah any real
yes
so whats z
so reals are 0
and z=7/2pi
z = x + iy
follow this form
a line
what
the result is infintie
x+7/2pi
whats x
yes R
is R
yep
thx
ys
there u go then
thcx
đ
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I get 0 here
am I right?
I just take out n^3 from each term under the cubic root
and take it infont
and I get 0-0
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Could someone explain how I can figure out of T is one to one
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@gloomy valve
On the contrary, T is one-to-one if dim(image(T)) = 2
Or in other words, if the output can produce two vectors that are linearly independent
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A conservative force field in n dimensions is a function F: R^n â R^n for which there exists a function V: R^n â R such that F = -âV. In this case, V is called a potential function.
(a) Consider the force fields F1 and F2: R^2 â R^2 defined as follows:
F1(x, y) = (y, x), F2(x, y) = (-y, x).
Determine whether F1 or F2 are conservative forces and, if so, find their respective potential functions.
can anyone help me with this
Iâm too young to know the answer srry
appreciate it
well you want to find a V : R^2 -> R with - grad V = F1
first off, what would grad V look like ?
@nova whale
yeah -grad V is that
yh
so we have $$\begin{bmatrix} -\pdv{V}{x} \ -\pdv{V}{y} \end{bmatrix} = \begin{bmatrix} y \ x \end{bmatrix}$$
yh
aPlatypus
wait so you found it ?
seems to work at least
idk quite how this is t rue
I mean if you found a suitable function you're done
but anyway, the general method from there is to solve those two very little partial differential equations
$$\begin{cases} \pdv{V}{x} = -y \ \pdv{V}{y} = -x \end{cases}$$
aPlatypus
those two things have to be true at the same time
that's what you do in general also
ofc I plugged in the functions of your exercise
ok sure
$-\nabla V = F_2$ means that $\pdv{V}{x} = y$ and $\pdv{V}{y} = -x$.
If we integrate these two equations, we get that $V(x, y) = xy + F(y)$, and $V(x, y) = -xy + G(x)$ for arbitrary functions $F$ and $G$
therefore, we get that $xy + F(y) = -xy + G(x)$, which is impossible
$F_2$ is not conservative
aPlatypus
yeah sorry I thought of F_2 the finite field for some reason
there
yeah
if you intergrate the nabla disappears
mmh ok
this one makes a little sense
why is V(x,y) two things @sullen island
@sullen island i have anothing question as well, just ping me when u r on
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how do i do this
well im pretty sure it was sum like find the prime number or sum
i didnt really understand what they were on about
what is 16 as a power of 2
4
yeah, 2^4, so whats 1/16 as a power of 2
$\frac{1}{x^a}=x^{-a}$
if i did tht right
Aâ¤Ă
say what now
oh
LMAO
i plugged that into calc
ok nvm i did that way wrong
oh i get what ur asking
yeah it flips the exponent
to neg
so what is 1/16 as a power of 2
well, if 2^t=2^(-4) theres only one thing t could be
if this was a bigger number tho like howd i go about it
cuz like tis a little number so its just sum yk already
logs usually
so the t is -4
it is
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How do i solve this
i tried doing i but got like a fraction rthen having to devide by that fraction or sum and was a whole mess
log to the what base do you think will work here?
Can we see your work?
i was doing 7xâ ln(3) = ln(4)
so far so good yeah?
then divided by ln(3) on both sides
sure
so i got 7x = ln(4)/ln(3)
.
hm?
where did u get ln(1)?
divide both sides by 7 instead
so
7xâ ln(3) = ln(4)
then divided by 7 on both sides
(xâ ln(3))/7= ln(4)/7
?
You're done. Divide by 7,
x = ln(4) / 7ln(3)
Willy the Explorer
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
\frac
its going to be log base 3 and argument 4
once you do change of base
but yeh, kaynex is right
,w ln(4)/(7ln(3))
$$\log_3(3^{7x}) = \log_3(4)$$
$$7x = \log_3(4)$$
$$x = \frac{\log_3(4)}{7} = \frac{\ln4}{7\ln3}$$
b0ngl0rd
good illustration of change of base actually
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Pretty sure how to do this just making sure
I assume you have an answer in mind then. Could you show us your work?
I am thinking itâs the 8i
8isqrt(7)? Show your steps just to be sure
Actually nah not necessary
8isqrt(7) is correct
Since you're apparently not here I'll just close this channel
.close
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@restive river Has your question been resolved?
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!status
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2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
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7. None of the above
@burnt tide Has your question been resolved?
<@&268886789983436800>
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Consider the following function:
f(x) = x^2 +2kx + 1 where k is a real number
For what values of k does f-1(x) have two assymptotes?
Express your answer in the form a<k<b or k<a,b<k as appropriate
ive found the inverse function: +/- â(x-1+k^2) -k
but first the function has to be one-to-one, so idk
yeh same. also dont quadratics have no asymptote anyways
For a second there I started to doubt whether I knew the definition of "asymptote"
i wonder if it means 1/f(x)
Hmm, that's worth wondering but very unlikely
ohh that could be very possible
Though in this scenario it's the only feasible explanation
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im struggling to get the minimum part
im very confused why the GS orthogonalisation has v'_jw_j on the bottom
shouldn't the bottom be w'_jw_j?
@jaunty mantle Has your question been resolved?
Huh interesting
https://math.libretexts.org/Bookshelves/Linear_Algebra/Book%3A_Linear_Algebra_(Schilling_Nachtergaele_and_Lankham)/09%3A_Inner_product_spaces/9.05%3A_The_Gram-Schmidt_Orthogonalization_procedure
Looks like this has a similar proof too
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Anyone good at Taylorpolynomials?
I wanted to double check with you guys and ask if the only mistake I made was the "+" sign in front of the second term (when n=1)?
Don't get demotivated by language barrier. They are asking for the Taylor polynomial of degree 8, with centre at x0 = 0.
I used this by the way.
your 2nd term (with x^4) should have a minus
yup, realized that. Anything else?
rest sounds good
Like.. it's correct for me to include the third term yes?
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Hi guys,
Which would be quicker, to row a boat 5 miles then turn back and row 5 miles in the opposite direction when there is no river current, or to do the same thing when there was a current (meaning you'd be rowing downstream for 5 miles, then upstream for 5 miles the other way)?
well, it would depend on the speed of stream and the boat
hmm, I wasn't given those in the question. I was just told that you can row at velocity v and the river has velocity x
$T_{rc}=10\cdot\frac{x}{x^{2}-y^{2}}$\$T_{nrc}=\frac{10}{x}$
B-eard
These are the times assuming x to be speed of boat and y being speed of current
rc- river current
nrc- no river current
ah ok interesting, I just assumed that any speed gains caused by rowing downstream would be cancelled out when you turn back and row upstream
so I assumed they'd average out and both scenarios would take the same time
i was thinking about set destinations, this a different scenario
So here is the exact question
You are an excellent rower and you can row at velocity v on a lake in your hometown. Today you decide to row on a straight section of the river Thames. The Thames is flowing out to sea at a velocity of x. You always row a distance of y meters from the boathouse then turn around and row back.
ia) Does the round-trip take you more or less time on the Thames or the lake?
right, that's not different, i'm just confused af
$\frac{1}{x}>\frac{x}{x^{2}-y^{2}}$\$-y^{2}>0$
B-eard
If we assumed T_nrc>T_rc then we would arrive to a contradiction
But yeah this is true if and only if x^2>y^2
wish I knew how to put that into a calculator đ
ok, I must admit, that is beyond me. So, I guess I was wrong to assume that the differences in speed caused by rowing down/upstream would average out?
wait
Let me explain you
assume speed of boat to be x
and the speed of river to be y
So, the effective speed downstream would be (x+y) while that upstream would be (x-y)
you follow?
yeah
that's what I initially tried, so I somehow ended up with the formula: 2y/((x - current) + (x + current) / 2, with y being the distance to the boathouse and x being the speed of the boat
$T_{rc}=\frac{5}{x+y}+\frac{5}{x-y}=5\left(\frac{1}{x+y}+\frac{1}{x-y}\right)=5\left(\frac{2x}{x^{2}-y^{2}}\right)=10\cdot\frac{x}{x^{2}-y^{2}}$
B-eard
that is really unreadable without latex
sorry yeah, I haven't used latex before
ok so the formula at the very right of your post is what we use
yes
10 x ( x / x^2 - y^2 )
if you don't use latex better use * to show multiplication
Okay, so similarly you can calculate time whitout river current
speed upstream as well as downstream is same
When you row downstream the current saves you time proportionally to time it takes, and speed of the current
When you row upstream, "the time it takes" is increased
so it doesn't cancel, it's universally worse if there's any current
no
ok why
if the speed of boat is less than the speed of current, then T_rc is less than T_nrc
$x^{2}<y^{2}$\$T_{rc}<T_{nrc}$\$\frac{x}{x^{2}-y^{2}}<\frac{1}{x}$\$x^{2}>x^{2}-y^{2}$\$0>-y^{2}$
B-eard
it's safe to say this never happens
so the tldr is that if there is a current, the additional speed you gain from rowing downstream isn't as much as the speed you lose from rowing upstream?
yes
ah ok interesting
the time increase is more than time decrease more accurately
because the current has more time to to affect you
oh that makes sense!
so kinda like those things at airports, the flat escalator things that you walk down
if you walk down them, you exit quicker and thus the speed increase from the escalator had less time to affect you
but if you walk against them, they're slowing you down and thus is takes you longer to reach the end, meaning they had more opportunity to slow you
I think I get it
exactly that
that's interesting. Thanks both, you guys helped a lot!
guess we're done here, but idk how to unoccupy this channel đ¤
type .close
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n^3 + 121 is divisible n + 11, what is the greatest value of n?
hi
you can use this
ax+b | P(x) then ax+b | P(-b/a)
(just so you know if P(-b/a) is a fraction just take the common denominator and write it as 1 fraction and then ignore the denominator)
What step are you on?
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2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
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@brazen star Has your question been resolved?
wait i've done it, i forgot to close
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mb
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How is this equal to e??
What would you have thought it is equal to?
1^infinity which is an I.F
Many would say 1
By saying this is 1^infinity, you are taking the limit of the bracket first
How did we get rid of the I.F though and got e
ik
I mean i don't know what the limit is equal to (i got I.F) I couldn't get rid of it
What's your definition of e?
A constant approx equal to 2.7 đ
Well then you can take this limit as the definition of e
It converges to some number, we call that number e
So there's no proof?
If you have no other definition of e then no
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a right triangle with one acute angle of 45â and the hypotenuse of length 10 units, find the lengths of the other two sides (the legs).
using trigonometry
Did you draw a diagram?
That should be your first step
okay
Draw a diagram with that info
You can use paint to draw it and send a screenshot of
sin(a) = opp/hyp, and cos(a) = adj/hyp, so you can sub in the values for the angle and hypotenuse, and then solve for the unknowns. On 45° right triangles, the sides should be the same length, so if you get different answers for each, you know something went wrong.
i don't know what is opp and adj... i know only base and perpendicular
If you know SOH CAH TOA, you can find the ratios based on the angle
I dont know what does that mean
i want to find only the legs
not ratios
You would use that to find the values of the legs
If you are using trig
i'll try
If you don't know that, then you would use properties of a 45 - 45- 90 special right triangle
what should i name the opp and adj
It's in relation with the angle
i should name opp and adj as x and y?
Yeah you can do that
ok
can i solve the problem using pythogoras
?
so both sides will be x
right>
?
You can do that too
wait i'll do that and send the pic
There are multiple different ways to solve, but you said solve using trigonometry
But i want it using pythogoras now... pls?
like whatever method is easy we can do...
Like I said, there are multiple methods to solving it. You specified trig, which was why I started off with giving you SOH CAH TOA
Yes that's right
I'm sorry for that...
tyvm now can i .close the chat
?
If you're done with it
i'm new i don't know that's why
will the bot ask me whether i got my solution or not?
No
okay
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.When you see this, you are good
ok
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I've completed all of my exercises in Basic Mathematics so far, but I'm struggling with this proof.
If n is even, then (-1)^n = 1
Working with what I know so far, I can't seem to figure it out.
If n is an even number, then by definition, n = 2m where m is any positive integer.
Then,
(-1)^n = (-1)^2m
So, (-1)(-1)... (-1)(-1) for a total of 2m times.
Then, (-1) will always be multiplied by itself a multiple of 2.
Basically, in the lowest case, if m = 1; then, 2m = 2
So, we'd have (-1)^2m = (-1)(-1), which is positive 1 by definition.
So, whether itâs 4, 6, 8, etc., we will always be able to split it into pairs of:
(-1)(-1).
For example, 4 would be (-1)(-1)(-1)(-1)
Associating, = [(-1)(-1)] * [(-1)(-1)]
Which will be 1 * 1, which is always positive.
This would obviously hold for all even numbers, since it will always be possible to put it into pairs of 2.
My issue is that I canât figure out how to formulate it with the tools I have.
All we have so far is the basic properties of addition and multiplication (that theyâre associative and commutative). We have the distributive property and the usual proofs with them. We have the laws of exponents. We have proved the sums and products of negatives and positives.
We have proved, for example, that a^2 is always even if a is even. We have proved that a^2 is always odd if a is odd.
In a sense, I can âseeâ whatâs happening, but I just canât figure out how to write it down
If itâs possible, could you guide me toward the right answer rather than just explicitly giving it?
We have the laws of exponents
@gilded coyote you can use one of those
particularly $a^{pq} = (a^p)^q$
Ann
Okay, I'll try that, thank you.
Another way would be splitting $(-1)^{2n}$ into $(-1)^n \times (-1)^n$
Frosst