#help-17
1 messages ยท Page 105 of 1
the larger function subtracted by the smaller function
and where the intersect is your bounds
Hi, I have an algebra question, at least I believe it is
doesn't that give the area enclosed between the two equation?
hi there, can you open a new channel? This one is occupied.
correct. Is that not what you're asking for?
that would gice this no?
yeah correct
I need the area enclosed by the curve, the line, and the x axis
is that possible?
if it's too advanced, i'll probably just get back on this problem in the future.
just curious, what course is this for?
I don't know if I grok what you're asking for. ๐ฆ
Can you highlight what area you're actually lookin for like you did above?
Wait, nvm
it's just the area of the curve and the x axis - the area i highlighted.
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ah ok that makes more sense lol.
Sounds like you got it!
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could someone help me with this problem? honestly i have no idea what im doing rn
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Yo
Technically the question is a physics type of question
but it isnt part of physics class
nor have I taken physics before
Its more of a figure process physics thing for engineering class
So my question is about the conversion
The equation PE/1 โข 1/m โข 1/deltaH = g (considering PE = m * g * deltaH, and that I need to solve for g)
And g needs to be in ft/s^2
on the left I replaced J with kgโขm^2/s*2
and on the right I replaced J with Nm
So either way
I'll get kgm in some sense
but I feel the right side is easier to understand my question
So if I take out the m
I have 901N
then I can replace N with kg mass and to 1m/s^2
so I was looking at how I can change / get rid of lbm and I was thinking
if I switch N to kg mass, is that the same as lbm?
so I could convert pound mass to kg mass
and would that cancel out or would that leave me with a kg/mass answer?
Honestly these problem sets with units are out of my repertoire so I really struggle with them for some reason
Actually better yet
if someone could explain to me the connections I'm missing with lbm and lbf that'd be nice
because I feel those are a bit confusing to me
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sorry last trigonometry question i promise
yes! i saw a video on this just now
and i was wondering
if i do this
3x = pi/2,
x = pi/6
i think from this you only get answers in 1 quadrant
not a general solution
i think you can do this though
if it asks general solution then no
3x = pi/2 + 2'pi'n
x = pi/6 + 2/3'pi'n
same as what i said
i wrote wrong i think
ye
because we have sin(2x) = cos(x)
in this
which we convert to sin(2x) = sin(pi/2-x)
and then we can move the x over and get 3x = pi/2
it can also be - pi/2
and then we have 3x = pi/2 + 2 pi n
thats a part of the solution yes
so x should be pi/6 + 2/3 * pi * n for all solutions no?
ah ok yeah
3rd
i mean
not 4th
where both negative
this answer you got from both positive
for the other answer
i would not the substitution method but
2 sin x cos x
2sinxcosx = cos(x)
move it over
2sinxcosx-cosx = 0
cosx(2sinx-1)=0
cosx=0 and 2sinx-1 = 0
cosx=0 gives x = pi/2, 3pi/2
sinx = 1/2 gives x = pi/6, 5pi/6
ye
what would the union look like? i thought union only was a thing in graphing when expressing the range/values?
although I guess this is values too
oh yeah because you ust add 2
and get 3pi/2
but the other one is not the same no? because pi/6 + pi would give 7pi/6?
yea its not
union i was talking about was
one solution is 2n+1 pi/2
other is n pi +(-1^n) pi/6
because when n is even
we are adding pi/6
when its odd
we are subtracting
if we get that we use this form
okok
i cant seem to think of a way to write them together rn
youll miss solutions
5pi/2-x
cos(pi/2-2x) = cos(x)
no thats same thing
and then in the unit circle look for where those values occur again?
couldn't I just say that sin(x) = 1/2 which also occurs at 5pi/6?
and the same for cos?
or no it's gonna equals the same thing
but your eq says 3x=pi/2
ok yeah
so its not convincing
just expand
what would you do then?
that's what i suspected
3sinx - 4 sin^3x
wait what
i do not know but would like to know ;D are there any videos online for this?
idk
Khan academy.
yeah that one i know
you get a cubic in sin x
using sin x as y
3y-4y^3+2y^2-1=0
you solve this
and use the solutions lying strictly between -1 and 1
legit have no idea how to solve that with the 1 being there imma be honest with you
otherwise i could probably factor out the y
like the only way i know to solve those is long division
then solution doesnt exist
but there's no denominator(?)
yeah i think thats what my uni teacher said to
like look here
oh like -3x^3 + 3x^2 ?
which will give a solution
-3 + 3 = 0?
okok that checks out
but if i were to get sin(3x) = cos(2x) tomorrow on my amazing test that i don't feel prepared for
and i will check out angle addition but like yeah
do you think they'd hang me alive if i do sin(3x) = sin(pi/2 - 2x)
idk i have literally never used that method
i mean its university level and we're probably expected to know this, issue is i didnt do math for 5 years and remember 0
for trig eqns
well lets see if it works ,D
which is one solution
from the cubic youll get
root 5 -1/4 as a root
which is sin 18
18 degree
yeah the same
cause pi/10 is 18
and then i think i can say
- 2 pi n
and also do 2/5 pi n
to get the other solutions
better than 0 XD
nevermind
no
from cubic youll get a root 5 +1/4 aswell
2pi/5 yes
youll also get pi/2
wouldn't we get pi/10 + 2pi/5 -> 5pi/10 which is pi/2
as a solution
hmm
pi/2 coming from the fact that the root of the cubic was 1 aswell
ok so what solution am i missing?
cubic will guarantee you all answers
i have pi/10, pi/2
2pi/5
ok so we set n to 2
n?
pi/10 + 4pi/5 = pi/10 +8pi/10, = 9pi/10
yes but when n is = 1 you get that
i think
wait
look
pi/10 + 2pin/5
when n is 0
we get pi/10
when n is 1
we get pi/2
when n is 2
we get 9pi/10
cos 18pi/10 is 4th quadrant
cos pi/5 youre getting from this
sin 27pi/10 gives you
cos 7pi/10
sin*
cos 3pi/10
definately not equal
cos 3pi/10 and cos 2pi/10
using cos (-x) = cos x and sin (pi-x) =sin x
oh wait
sin 3pi/10
ok youre right
its is 2/5n
IT DOES WORK!?
ye
holy macaroni
had to check
ok that's good news
i will still try to learn angle addition because i want to use the "good" techniques
but while im trying to learn this one is a little easier :p
for trig equations factoring is the best methof
yeah it does seem to be very good
do you have any recommendations for good geometry problem videos?
my own gemetry is ๐
because we're expected to know all these formulas but when i tried to look online for like precalc / calculus geometry it's really lackluster compared to the problems in the last exams..
like this one
im not entirely sure what the idea is here
a chord in the unitcircle is seen from a point on the circle with the degree of 120, (see figure), decide the chords length
so there is the "randvinkelsats"
is this correct?
that's what i was afraid of
my lines u mean?
but are there rules that the opposite corner in a quadrilateral always is opposite angle?
so middle angle 60
and radii are 1
got it
no problem dear sir
so what you do is you join it to the top
yes b=2x is correct
then you apply sine rule
cos no?
c^2 = 1+1 -211 cos(120)
ah wait
its 1/2
its the a/sin A = b/sin B = c/sinC right?
just plug values
sin 120/sin 30 =x
sin 120 is cos 30
cot 30 =x
x is root 3
same answer
yes
i know it's a bit further ahead
ok so
isnt sin90-x also cos x?
ok but then i think i understand this one
as long as the point in the middle connects to the same lines as the other angle it's gonna be double?
wut?
im not sure how you get it otherwise
oh this
A central angle is twice the size of an inscribed angle if they span the same arc. Discover the inscribed angle theorem, its uses, and how to prove it.
but im having issues seeing how it works with this problem..
angle at centre is double angle inscribed
this is correct
ok awesome
okok
and how would you approach this one for example?
translation on its way
20 meters of steel wire must be used to enclose a flowerbed in the form of
a sector of a circle with an angle ฮฑ between 0 and ฯ and radius r (see figure). For
which radius of the circle sector is the area of the discount the largest, and what is it
maximum area?
i assume we want to set up a function right?
uhh
so
is the area of the flowerbed the largest
yeah got it
rabatt means flowerbed and discount XD
yeah so 2pir is circumferenece
+2r
,thats whole circle
yep
ohhh ok
write that down kek
i think i can remember it
ok so normally entire circumference is 2pi*r
yep
and you set that equals to 20 for the length of the steel wire?
adding twice the radius
then yes
because thats how much wire we have
now
r+ rpitheta=10
r pi theta = 10-r
theta = 10-r /rpi
okay?
and wait wait you say r twice because of the radius apart from the circlesector right
just making sure im with you
yes
yed
im with you then
yes
yep
also from here just r theta = 10-r/pi
well this works
so it cancels
pi and r
r(10-r)
when is this maximum?
yeye
yes
here
ok then i think im with you all the way
am gm inequality, another term i've never heard of ;D
thank you so much for all of this help btw
did you have any recommendation for videos that target these kind of geometry problems?
i dont study from videos kek
XD
books>
like the issue with my uni books is that the problems dont have the steps to the solution, just the answers
all this was in my school curriculum kek
uni for me means different kek
uni is after college
these problems are my grade 10
ah yeah this is probably college for you
no lmfao
like 19 year olds?
XD
i mean we did have this back then too
its just that we're supposed to still know it
bro frogor
lo
literally was wondering what happened when i multiply negative values
i was 90% sure it was gonna be positive
๐
but now i have to continue as if i were just in grade 11 or w/e u said it was
ye
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finding gradient using limit method of $ y = \frac{1}{x^2}, x = 2$
$ y = \frac{1}{x^2}, x = 2$
chlamydia
any progress?
the problem is that what I call D, the y of x delta minus y of x, gives a fraction
so D / dx is complicated and i get lost trying to get to the answer which should be -2
i can however tell the pattern that when we expand y of delta x, and subtract y of x, we have the coefficient of delta x being -2. This coefficient is always also the final answer
but for the previous exercises i was able to get to the final equation through algebra and then plotting limit of dx -> 0 to get the answer but for this exercise I wasn't able to
basically we have $\frac{\frac{-2dx - dx^2}{1+2dx+dx^2}}{dx}$
marty
slope
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How can you solve an arg like that?
@languid venture Has your question been resolved?
<@&286206848099549185>
Ahh ok I try
What about the fact that its all =1?
what should be? its just an equation. 1 = arg(i)+2arg(z). solve it.
Rught ok I try
@languid venture Has your question been resolved?
Since z=x+yi how can I calculate arg without knowing x and y
the point is: you posted just a small part of the exercise, so it is nearly impossible to help you. What is asked in your example?
It gives me options to reply about the solutions of the exercise
you know the left side, you should know arg(i) so you should be able to calc arg(z).
Like this?
yes, so you can calc arg(z), but you still havent said what the goal of the example is.
It asks if the solutions are a line a circle or a uhh
Not full line
It also says there are many solutions?
@languid venture Has your question been resolved?
<@&286206848099549185>
Yeah?
Can you help me choose the right answer
It asks if the solutions to that arg are a line a circle a not full line
Why?
Which book is it from?
Its a old exam not book
How do u get a circle from this
Yeah but italian
Yeah I'm thinking
I can tell vorrect option
??
Did u figure out
?
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So if we are converting the parent function $\frac{6}{x-3} + 5$ to the child function $\frac{6}{-3x-3} +5$ . IS THIS reflection over the y axis or the x axis. And is it a vertical dilation of 3? Or is it a horizontal dilation by a factor of 1/3? Or is it horizontaly dilated by 3?
ahaan
<@&286206848099549185>
Had posted this an hour ago
in a diff channel
<@&286206848099549185>
how?
think about it
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โ
@formal gazelle Has your question been resolved?
so basically for this question if you cant rememeber it, I try to roughly sketch it
Its kinda hard to sketch this ngl
I would just plug in points
hmm ok so the parent function x is a -3x in the child function so y-value when x is -1/3 would be the same as y value when x is 1 in the parent so if any arbitrary point on the parent were like (x,y) then a point on the child would be (-x/3,y)
so then you can see how it changes from the (-x/3, y)
does that kinda make sense?
no?
wait a sec lemme see if I can find something
basically use that
does that help?
if not I can help break it down
look at your parent function as f(x)
how would you represent you child function in terms of f(x)??
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How can one calculate trigonometry functions without a calculator?
painfully
But it depends on the function and input
what question is it?
Lets say for an example cos 800ยฐ = 800-360*2 = 800-720 = cos 80ยฐ
so cos 80ยฐ without a calculator
damn
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I'm not sure how to define x in terms of theta, can anyone offer any insight?
$\cos^{2}\theta+\sin^{2}\theta=1$
b0ngl0rd
I factored out the 16.
so you got the 1 - sin^2 as the identity, which works
you gotta find what you replace x with.
As to how this is derived I am very confused.
Not sure how to put x in terms of theta
trig sub.
look at your work
you'll see x/4 appears
but thats slightly confusing, thats why i was trying to show through the identity how to get it
$16\cos^{2}\theta+16\sin^{2}\theta=16$
b0ngl0rd
square root the whole thing
$\sqrt{16\left(\cos^{2}\theta+\sin^{2}\theta\right)}=\sqrt{16}$
b0ngl0rd
$4\sqrt{\cos^{2}\theta+\sin^{2}\theta}=4$
b0ngl0rd
that constant is the multiple you need for the substitution
$\sqrt{r^{2}-\left(r\sin\theta\right)^{2}}$
I do see x/4, how do we know that was equal to sin? (thank you for showing me this other clever trick as well).
because the identity matched the form, all that we needed to do was scale the identity by the radius of the semicircle we are working with
sqrt(16) = 4 = radius
b0ngl0rd
Is that because somehow the 4/x matches the reciprocal identity for sin?
no. the reason is exactly what your work shows, that the radius scales x, specifically by a factor of 4
thats why we take x/4 = sin theta
then to get x we multiply
So basically x is always going to be a*sin(theta)?

@grand void Has your question been resolved?
Did the top need to be simplified to 4cos(theta), and then make the subsition or should I just make the subsitution from the very beginning on x?
if you know the substitution you should be able to do it from the beginning with no work done.
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Need help with combinatorics
Is there a formula to find how many different variations of two dice equaling a certain number
say I want to find how many ways I can roll two dice to equal the number 7
is there a formula for that?
There's a method called "stars and bars", which can solve it, and some problems like it
What's your thought process?
But I thought you wanted the number of ways to roll a 7
In this case, it's also pretty easy to count all of the cases
1+6,2+5,3+4,4+3,5+2,6+1
Sure. So to connect this to a more common problem:
You want the number of positive integer solutions to the equation x + y = 7
Let's say I take 7 stars and 1 bar, and put them in a row like this:
***|****
That permutation of stars and bars corresponds to the solution 3 + 4 = 7
So every arrangement of stars and bars corresponds to a solution to the equation
The question is NOW:
How many ways can I arrange 7 stars and 1 bar?
Oh wait I am making a mistake. 0s are allowed in the solution, when using this method
|*******
Is 0 + 7 = 7
thats impossible
But obviously that can't happen with dice
This seems to be a pretty different question
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Hey can i get help for a linear algebra question?
sure I can try to help
so i can send you my work
but warning its a whole page long
but please tell me if i was on the right track
and these are the answers for this question:
ok
this is my work
but i checked and im pretty sure my answer doesnt line up with the answer given in the answer key
and i sent the answers above
Right so you just want to change it into I think it's called identity matrix
yes thats what I thought shoulvde been done in this question
I wrote it in terms of a augmented matrix or you could say identity matrix
is the bottom one the final matrix?
you want to make the ones at the top also 0
thats why I need help from someone who could help solve this questionb
so you can get top row 1 0 0 0
next 0 1 0 0
and so on
the matrix is basically a system of equations
but i dont know how I could do that
it seems too complicated to get the top row 1 0 0 0
is it possible if you could show me the proper steps to solve this system of equations?
then I could compare it with my work?
you have to work you down from the first row make the numbers under the first ones all zeros
you want to make it one so it's easier to cancel out the ones below
one more thing I think I could do here is turn that 823/105 in to a 1 and i know how to do that
yes exactly
could you show me the steps?
im gonna do that right now to see what answer I get for w.
so divide the first row until first is 1
Btw I do suggest simplifying your fractions
that too
Yes thats one thing
ah yes
I tried to do that sometimes
but then i stopped simpliyfying
overall do all my steps seem correct?
cuz if they do Im pretty sure my final answer will still be wrong.
try to get the diagonal ones to 1 and all the others below that to 0
bro
then you have to get all the ones above it to 0 too
What's this number here?
1760/90
No need for RREF, you can back substitute
thank god lol
but overall do you guys think my steps seem correct and on point?
and if not could someone maybe try this question and show me their steps?
you need to finish but other than that I think so
id really appreciate it
I can't really show you rn but I can walk you through it step by step
like can you take a picture of where your final matrix is now?
first step is to simplify the fractions
can that be simplfied?
That number?
I think it would be best if you simplified before going forward
right
so that way the numbers are easier to work with
that says 2800/90
so that could be simplified
i cant go back and simplify tho now
That's the first mistake
It might be a calculation error
or let me check
,calc 2 * (625/90) - 5
Result:
8.8888888888889
,calc 2800/90
Result:
31.111111111111
chill
yea your right
my bad
i cant
ive been working on this for 20 mins
or 15
or even 30
i made a calculation error
it fine I make them all the time
i know but i have a midterm on this tmmrw
try simplifying the fractions to make calculating easier
thanks your right
Definitely the not simplifying fractions messed you up
yeah
if worst comes to worst just write out a system of equations
if i was trying to row reduce, could i still find the values of each vairable with a matrix that looks like this
thats basically all it is
wdym
so this is the final matrix i got
but with using the info in this final matrix
can i still derive the values of x,y,z,w
not if they are calculated incorrectly
If you did algebra correctly
so is it not possible to derive the values of x,y,z,w if I did the algebra wrong?
you can think of it like 0x+0y+0z+1w=(number)
shouldnt i still be able to derive the values
even if it gives me the wrong answers?
the matrix is sorta just a system of equations
You'll get wrong values that wouldn't satisfy the system
yea ik thast
You'll get a set of values for x, y, z, w but it wouldn't be correct
ohh thats what i wanted to know. So therefore, I would get the values, but the values just wouldnt be right
ok thanks
thats what i wanted to know
unless your teacher specifically asks for using the matrix I would just use a system of equations
Because I was just confused as to whether or not a system of equations has to be in rref in order for you to derive the values of varaibles
oh you mean like simply using subtituion method or elimination?
cuz yea im def gonna do that
substitution and elimination
but he most likely will ask us about ref and rref
well if you think about it like the first row is 90x+90y+80z+12w=124 (im making up numbers) and the other rows like that and your just solving it in a different way
yea that makes sense
you can think of it like a fancy way of writing it
ref and rref is the cancer way to solving for variables i feel like
it's different
Elimination is just gaussian elimination
what your doing basically
its just the row reduction things
sure
this one will also be on my midterm tomorrow and it involves financial mathematics
I can try but i might not know how to solve
Is there someone who might know financial mathematics?
but yea please try if you can
i need help with specifically b
and d
for this question all i know is that you can use annuity formulas or you can use sigma notation to solve this.
Yeah with gaussian elim, you multiply some row then add/subtract it to another, same thing with general elimination because you would take one equation, multiply it by some value to then add/subtract with some other equation to eliminate variables. The matrix is just the value form of general elimination
yeah imma be honest im in middle school idk how to solve financial mathematics
ur in middle school and u know how to do ref and rref?
uh yeah