#help-0
1 messages · Page 576 of 1
#old-network physics server
no. your root starts out as sqrt(n^2-i^2)
(3x)^2 -2^2
any one know how to solve this integral with the given two suggested integrals - i tried u = 2r/a as a substitution but i don't think my solution is correct
C is just some constant
main problem is if i use u = 2r/a for the e^-u i don't know how to handle the 1/r term infront
Someone please help
-_-
@daring rapids move to some other channel
Oh sorry
@cold mica maybe you can rewrite u=2r/a to r that way you can just put it in 1/r and get rid of it
well solving that for r gives r = au/2 but 1/r then means the integral has 2/(au)
which means i have 1/u e^-u (once i take out the constants)
which is not quite right
mm not sure I don’t have pen and paper on me right now, maybe you could partial integrate it though
thats beyond the level im at so i dont think thats going to be the solution
Ok you can just rewrite your function if that’s the case
what do you mean
e^(-2r/a) = ... * ...
I’ll let you think about it first
Keep in mind that the 2 and a are constants, so if you have e^constant you can move it out
well thats = e^(-r/a)*e^(-r/a)
but not sure if thats what you meant
r is not a constant don't forget
thats the subject of the integral
unless you mean factor out e^(2/a0)
leaving just e^-r
Yeah that was my initial plan but it doesn’t work nvm
tho im not seeing it still since i have one in the denominator and one in the numerator
Wait
Did you forget to change the dr part?
since you get du = 2/a dr
Or dr = 2/a du
This is a constant you can move it out
no i didnt forget that
Given the density d of particles, what's the average distance between two particles?
Channel taken
ah
i might've solved it @spring harbor
What did you do?
So the question was wrong?
possibly but not sure yet still checking it all
Alright that’s possible then
ik this is a math server but can someone help me with history?
ik this is a math server
ok starting off well
but
oh no
can someone help me with history
- The help channels are solely for help with math, so feel free to post your question. Asking whether you can ask a question or if anyone knows about some specific topic is unnecessary, so please try to avoid questions of that nature.
nope you'll have to find a different server
my assumption is that
part a the displacement = 10 meters
part b professor buske is 10 meters away from his mailbox
i get 7.5 for 1
negative
then i get -2.5m for the second
same for both
do you think you know?
tell us what you have and we can say if it's right
I think it's false
@ionic jewel how did you get 7.5 for part a
integral from 2 to 4
it is false, but do you know why?
My guess is that it's because B is from 1 to 50 not 0 to 50
I'm still very confused with this topic so I'm not sure
that's right
i assume you know why that matters, but exactly
it would be true if it was 0 to 50
Thanks @ionic jewel
so if i have 5000 of something andsell it for 6500$, for 250 of it i pay 75$ how much profit would i get
what
???
number 1 crip gangster
can you phrase it more clearly?
they're paying 75 dollars for 250 units of something and they sold 5000 units of this soemthing for 6500 dollars
or post the original problem
is what it sounds like
post the original problem
you don't have 5000 units of it how did you sell that much?
as written it's 6500-75 with magic units appearing somewhere
So your cost price for 250 units is $75 and your sales price for 5000 units is $6500... and you want the profit for selling 5000 units?
this is a useless question to ask on this server
nobody ever has any clearer wordings
ikr
also how did you get -2.5 for part b, i understand you found the area for part a on the interval [2, 4], but idk how you got part b at all
i did integral from 0 to 4 lol
would that even work... ?
why not
so look i buy 250 apples for 75 dollars
you could make a lot of apple sauce with that
and then i buy 5000 apples and sell them for 6500 how much profit would i get
this is so confusing i know

you made it worse but i understand what you mean
How much money does it take to buy 5000 apples?
so you need to buy 5000 apples at a price of $75/250apples
well starting with this is good
how much to buy the apples?
i love magic the gathering
oh bye
how to find part b
delta x_k = 6 though right
yeah, now look at x_k*
the first one is at?
the picture divides it quite regularly
but it's not very standard
it's not a left sum or right sum
first one is at x = 14 and then from there it adds 6
but i dont know how to develop a formula for it
it's an arithmetic progression, right?
when k=1, we want 14
continue...?
k = 2 we want 20
i cant find a working formula where
10 + x = 14
10 + 2(x) = 20
10 + 3(x) = 26
because it's not 10
try starting with something other than 10?
A product in a shop is reduced in price by 20%. At this reduced price the shopkeeper makes only 4% profit. What percentage profit (to the nearest whole percent) does the shopkeeper make at its normal selling price?
How do i form an equation for this?
hmm actually this is quite conceptual
but you can say the cost price is c
and see what happens
@alpine sable OK, what two sides do you have, relative to the known angle?
You have the opposite and hypotenuse.
You correctly picked sine.
So, write the equation.
No.
Chai T. Rex
Chai T. Rex
bro
Chai T. Rex
Chai T. Rex
Chai T. Rex
Right, so what's the left side after you do that?
What's the right side?
No, without doing the calculation.
What does the right side turn into?
Chai T. Rex
What's the right side divided by it?
No, that's not it.
What's the right side?
No, that's after you try to change it.
What did it start as?
Right, and then what did it become?
Right, so let's go from there.
Right.
Divide by means you put what you're dividing by on the bottom.
Yeah, you were.
OK, so use your calculator now.
Yes, that's right.
So, that's x.
What's the next digit after that?
OK, so the next digit is 9, which is 5 or higher, so you go up one.
61.82.
You're right.
You're welcome.
It means arctangent.
Arctangent undoes tangent.
So, which sides do you have relative to the angle they're looking for?
No, probably not.
OK, so let's do the equation.
Chai T. Rex
Chai T. Rex
Chai T. Rex
Chai T. Rex
Chai T. Rex
$\tan^{-1}(\tan(x^{\circ})) = \tan^{-1}(\frac{23}{31})$
Chai T. Rex
OK, so we simplify the left and get:
Chai T. Rex
No, look at your answers.
No, don't put it in your calculator.
Look at your four choices.
One of them matches our last equation.
Right.
Well, write down the equations.
Chai T. Rex
No, that's the first answer.
Cosine is CAH, right?
What's the adjacent side length?
What's the hypotenuse?
Chai T. Rex
The first answer doesn't match what it should be.
Chai T. Rex
The correct equation, I mean.
That's the answer.
I'm asking you for the correct equation.
Sine is SOH, right?
What's the opposite of B?
No, the opposite side length.
Which side is 25?
Right, so it's not the opposite side.
What's the opposite side length?
What does adjacent mean?
No, what does adjacent mean?
Right, the leg next to the angle.
What does opposite mean?
Right, the leg across from the angle.
What does hypotenuse mean?
Right, or the side across from the right angle.
No, it's not always diagonal.
But it's always the side across from the right angle.
Chai T. Rex
Which of SOH CAH TOA is for sine?
Chai T. Rex
OK, what's the opposite side from B?
What does opposite mean?
What side is across from angle B?
That's next to B.
Right.
Chai T. Rex
What's SOH stand for?
What's the opposite side from angle B?
What are the two sides next to B?
OK, so write the triangle on paper with the letters and the numbers and the right angle symbol.
Let me know when you've done it.
Have you drawn the triangle on paper?
OK, look at the triangle on your screen.
We're going to find opposites.
First, we'll find the opposite of angle A.
What sides are next to angle A?
Cover those sides up with your fingers.
What side is still showing?
Right, so that's the opposite side of angle A.
Let's find the opposite side of angle B.
What are the two sides next to angle B?
OK, cover those sides up with your fingers.
What's the side you can still see?
Right.
Let's do the opposite of angle C.
What are the two sides next to C?
Right, cover those up. What's left?
Right. That's how you find the opposite side of an angle.
OK, so what's the opposite of angle B?
Right, what's the hypotenuse?
OK, look at the right angle.
What's the opposite side of the right angle?
OK, how do we find the opposite side with fingers?
No, cover up the sides next to the angle.
What sides are next to the right angle?
Where's the right angle symbol?
Right, so C.
What side is opposite the right angle?
Right, so that's the hypotenuse.
So, let's do $\sin(B)$
Chai T. Rex
SOH CAH or TOA?
OK, so what's the opposite side of B?
What's the hypotenuse?
OK, which angle is the right angle?
Which angle has the right angle symbol next to it?
OK, which angle is the right angle?
OK, what sides are next to C?
OK, cover them up. What's left?
Right, so what's the hypotenuse?
Right.
So, what's the opposite side of B?
What's the hypotenuse?
No.
What angle is the right angle?
What side is opposite angle C?
What's the hypotenuse?
So, what's the opposite side of B?
What's the hypotenuse?
What's opposite over hypotenuse?
Chai T. Rex
Chai T. Rex
Is that SOH CAH or TOA?
OK, now there's a trick.
C is the right angle, right?
How many degrees is a right angle?
Chai T. Rex
Right.
Is B the right angle?
OK, so we can't just use our calculator.
Is cosine SOH CAH or TOA?
What side is adjacent to B?
What's the hypotenuse?
What letter is the right angle?
What side is opposite from the right angle?
That's the hypotenuse.
Now, if 25 is the hypotenuse, it can't be the adjacent side, since that's a leg.
So, what's the adjacent leg to B?
What sides are next to B?
Cover up the hypotenuse.
OK, cover up the opposite and hypotenuse.
Actually, let's do it this way.
Let's find adjacent sides.
Angle A. What sides are next to angle A?
Which one is shorter?
That's the adjacent side.
Angle B. What sides are next to angle B?
Which side is shorter?
How do I compute this limit? Isn't it infinity?? But according to calculators it's -pi/40...
limit as x -> -inf of (1/20)arctan(5x/4)
@vestal hollow Well, you can move the constant out.
Yes, so lim x->-inf arctan(5x/4) should be -pi/2, which Google confirms. But I don't get how :( something about turning arctan into tan and then into sinx/cosx?
Chai T. Rex
$\lim_{x \to -\infty} \frac{1}{20} \arctan\left(\frac{5x}{4}\right)$
Chai T. Rex
consider the range of arctan and how the tan function looks
and/or properties of tan and arctan in general
and the limit should be clear
I see that it does approach a finite limit, but that's it :( how am I supposed to arrive at -pi/40 mathematically?
I didn't realize it was -pi/40 from the graph
But I did see that it went to a finite limit
Just not how
Sure, but the limit.
Almost.
Oops again
Tangent is the slope of the angle.
I'm sorry?
Chai T. Rex
It becomes larger and larger negative values.
I don't understand, I'm sorry :(
Wait
I plotted
Omg I'm sorry
Doesn't the limit not exist?
As we approach from the left, we get positive infinity
Right.
Hmm.
the range of arctan is (-pi/2 , pi/2)
Oh
Ahh, yes.
So it should obviously approach -pi/2
As we approach infinity
negative
brain is fried sorry, thank you both for being patient with me
No problem.
Okay yeah I get it now, thanks
hey
help me solve 29 please
I broke up the (-3)^(n-1)
which gave me
-3^n * -3^-1
parentheses around the -3.
this is a geometric series. do you know how to calculate the sum of a geometric series?
a/1-r
what is your first term and what is your ratio
(-1/3)/(1--(3/4)
the value of $\frac{(-3)^{n-1}}{4^n}$ at $n=1$ is not $-\frac13$.
Ann
how would I solve this equation p * (1 - p) = 0.1224?
yes, its not -1/3. how did you get -1/3?
-3^-1
where did that come from?
can we go in a voice channel please
But if not okay
so I broke up
(-3)^(n-1)
which is
you're over complicating this
-3^n*-3^-1
why would u substiture n=1
because the index of your series starts at n=1



this does not mean the first term is -1/3
yes, a would represent the first term
I see my mistake im used to just plugging in the number outside
but that usually works because the other number is to the power of n-1
is in reality it is (-1/3)*(-3/4)
okay thank you guys so much
is my method correct?
18) If x⊗y = (xy)^(1/2) then what is the value of (3⊗48)⊗9 ?
(3⊗48) = sqrt(144) = 12
(12⊗9) = sqrt(108) = 10.39230485
(12⊗9) = 6sqrt(3)
the idea is right, i didn't check the actual numbers
,rotate
I need help with c
@sullen nova Would you be able to help me, looks like you are ahead in the exponential part
So this is how far in it that I have
I derived the slope at the point -1/2,2 1/4 in the function
which the equation for the tangent at that point is y=3x+15/4
and I have the normal tangent that collides with point B the equation being y=(x+5)/2
And since I know these equations, how can I find the angle
for c
I'm just brainstorming some ideas
I got y =3x+15/4 through finding the derivative at the point of -1/2 in the parabola
@sullen nova dy/dx = -ay, rearranging, we have dy/y = -a dx, integrating both sides, we get ln(y) = -ax + k, which is just e^(-ax + k) = y, which is just y = e^(-ax) * e^k
this is the formula to find an angle made between 2 lines
I still didn't get it correctly
this is not the soluton
the answer for that is 45 degrees. But got it incorrect
so you got 45 deg?
No
So when i evaluate it into tan() = 1
I got 0.78
The answer is 45 degrees, but don't know how to get to there
,w tan^-1(abs((3-1/2)/(1+3(1/2))))
Yeah that is what I got
hi guys !!!
how can i produce this sequence ?
1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1,…
are you looking for an explicit formula or something?
am i understanding correctly that this sequence consists of steadily lengthening runs of ones and zeros?
hmm
so it goes with 4 ones then 4 zeros then 5 ones then 5 zeros and so on
is my understanding correct? @fluid valley
something to do with the sin funciton
yea exactly!!!
ok !!!
i think i got it
$a_n = \begin{cases} 1 & n \leq \mathrm{round}(\sqrt{n})^2 \ 0 & n > \mathrm{round}(\sqrt{n})^2 \end{cases}$
Ann
where round(x) is the function which rounds x up or down to the nearest integer, whichever is closer; for consistency you can say that it rounds half-integers (like 6.5 or 1.5 or 123.5) upward, but it doesn't matter here since sqrt(n) is never a half-integer
@fluid valley there you go
wow amazing !!! how did u figure it out ?
i noticed that the last 1 in every run was at a position that is a perfect square
that is, the 1-runs ended at positions 1, 4, 9, 16, 25 and so on
doesnt $\operatorname{round}(\sqrt{n+1})-\operatorname{floor}(\sqrt{n})$ also work?
Obstacle
does it?
lemme take a look
looks like it does! but it's shifted by 1 relative to my solution
since it is sequence question there are a lot of solutions to it
thanks alot Ann
first 100
[1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1]
algorithm
Start with index 1.
def gen(n):
n = n + 1
... res = []
... for i in range(n):
... if i <= round(math.sqrt(i))**2:
... res.append(1)
... else:
... res.append(0)
... return res
Note the extra 1 in front.
fixed
Yeah,
```python
code
code
```
For syntax highlighting.
def gen(n):
n = n + 1
res = []
for i in range(n):
if i <= round(math.sqrt(i))**2:
res.append(1)
else:
res.append(0)
return res
I think that still starts with 0, though, so it has an extra leading 1.
How do you get the range to start with 1?
range(1,n+1)?
yes
def gen(n):
res = []
for i in range(1, n + 1):
if i <= round(math.sqrt(i))**2:
res.append(1)
else:
res.append(0)
return res
i believe we can also use pascal for this
you can write an algorithm in basically any language for this
even brainfuck if youre so inclined
the what now
whats question 22
good morning
ok so try to use part a
Mani
@elfin ibex what do u need help with? simplify it?
yeah ^^
do u know how to simplify surds?
surds?
$sqrt{a}$
Mani
$\sqrt{a}$
Ann
roots
yeah
damn
i just dont know how to find the prime factor thing
do you know how to factor numbers in general
@elfin ibex are there any perfect squares that 45 and 80 are divisible by?
i just keep putting random numbers into my calculator
5
wait
5 is not a perfect square
^
but 45 is divisible by 5
and 80 is also divisible by 5, by coincidence
45 = 3 * 3 * 5 and 80 = 2 * 2 * 2 * 2 * 5
these are the prime factorizations
look up "how to factor numbers into primes"
2, 3 and 5 are primes
but i can also write this as
$\sqrt{45} = \sqrt{3^2 \cdot 5}$
Ann
and $\sqrt{80} = \sqrt{4^2 \cdot 5}$
Ann
;-;
@elfin ibex to simplify surds look for perfect squares that the number inside the surd is divisible by
but what perfect square is 45 divisible by
9
here read this
$2\sqrt{45}-\dfrac{1}{2}\sqrt{80}=2\sqrt{9\times 5}-\dfrac{1}{2}\sqrt{16\times 5}$
Mani
and then you can take split the surd and the perfect square using the rule that $\sqrt{ab}=\sqrt{a}\times\sqrt{b}$
Mani
okay.....
you should probably watch a video on youtube on how to simplify surds
square root are surds
alr for this eqution
square root is the symbol
for 10 what would it be?
is 10 divisible by a perfect square?
no
then its already simplified
oh
you cant simplify $\sqrt{10}$ further
i always thought u had to keep dividing until u cant anymore
Mani
na
okay thanks
nws
so now you can rewrite it as $-6\sqrt{10}+5\sqrt{90}=-6\sqrt{10}+5\sqrt{9\times 10}=-6\sqrt{10}+5\sqrt{9}\times\sqrt{10}$
Mani
whats $\sqrt{9}$?
Mani
3
im gonna go die
if u still dont get it, then u should watch a video on youtube and try to understand it properly
@alpine sable can u help me with this
can i dm u?
yea
oh
okay so the new polynomial can be represented in the form (x-(a-b))(x-(a+b))
right?
sure
k[x^2 - (alpha + beta) + alpha Beta]
whats the k doing there?
k = constant
exit ticket?
is that like a test? or is it not timed / open-book
also, i see you've selected choice A. was that intentional or random?
two different definitons given for h(x)
but luckily this won't affect the answer
use the formula for average rate of change for all the intervals
keep in mind the average rate of change of a line over any interval is equal to the slope
ok
@alpine sable i think its A
it was the graph being different no wonder yi couldnt solve it
Oops my bad
yeah that'd be correct
simplify tanxsinx first
its secx
tanx and sinx make sinx^2 / cosx
then find a common denom
get sinx^2 / cosx + cos^2 / cosx
that simplifies to 1/cosx
hello
Wait
any free to help
i thin k I know
Hmm can you try to explain?
I am checking my notes
Oki take your time
How do u solve sin(x)=cos(x/2)
This is occupied
what is the line equation on the second part of the graph?
Here
Used point 40,25 and 20,10
try 10,-400
what is this evaluated?
@vale tundra
my best guess is (10,-50)
how did you get the answers for the critical points?
@vale tundra Trust me
Hey everyone, the average tweet takes 10-15 seconds to type.. if a user joined Twitter in 2009 and has 70,000 tweets, how would you calculate the approx amount of time the user has spent on Twitter in total?
Omg itss right
How did you do it????
I have been stuck on this for forever
I did it like a week ago
I dont remember tbh
btw do you know how to do integral?
Does anyone know how I am supposed to predict the velocity of a bullet moving from one starting vector to an ending vector, given a static speed value and a gravity value?
Okay so i have this question on a mock exam paper that has rlly stumped me:
Two similar solids have base areas of 47cm2 and 199cm2. The volume of the smaller solid is 350cm3, calculate the volume of the larger solid.
How would I go about solving this?
@vale tundra (20,-75)
use equation of motion
anyone free to help me with some problems
what type of solid is this
wuld that be able to give me a velocity vector
Uhh
I dont know what kind of solid it is
It looks to be like, halfway between a pentagonal prism and a trapezoid?
Hold on
ye
To get the distance of two vectors, could I just add them together and then get the Length of the new vector
Ugh images take forever to sent with my internet
Just gonna delete that because I forgot to crop it
the length of the sum of two vectors is not necessarily equal to the sum of the lengths of the vectors
starting vector and ending vector are just angles
so we need two facts:
- if you scale a 2 dimensional figure by a scale factor k, the area changes by a factor of k^2
- if you scale a 3 dimensional figure by a scale factor k, the volume changes by a factor of k^3
we are given the these two figures are similar, so one must have been formed by scaling the other
in particular the two bases are also similar
assume the scale factor is k
that makes sense
lemme just
nvm Idk how to calculate the scale factor of 2d shapes
so write an equation relating the two areas
(area of base on left)*(k^2)=(area of base on right)
then solve
so l*k^2=r?
what is r and I?
left and right
yes
ok...
That is right
so to make k^2 the subject id need to add r to both sides, and divide by k^2?
Thank you so much
ohh that makes more sense
199/47 is 4.234, sqrt(4.234)= 2.057
thats k, so that means k^3=8.712
yes
which is the scale factor for the volume
yep
where did you get -30
I guessed
do you know why you got the x coord to be 4
Yes
AAAAAAAAAAAAAAAAAAAA
so plug in t=4 and compute
Ohhh
AAAAAAAAAAAAAAAAAAAA
So i need to find G(4)
yes
a^2 + b^2 = c^2
With C being the hypotenuse, and A being the length
To work out b, you need to work out c^2, and take a^2 from it
@stable dune
Take 25 fro 169
And that gives you b^2
Then take the square root of that number and you have your answer
Well, this is just worded differently
The base of the house is 6ft, which means the base of the triangle is 3ft
The hypotenuse is 5ft
Just plug those into the formula, just like before
ah but whats 6?
right
The problem tells us that the base of the entire house is 6ft
Which means the base of both triangles is 3ft
Considering that the hypotenuse is equal for both, and they share the same height
And as you are trying to find the height, you need to use 3ft instead of 6ft
Idk, you are the one working it out
thats what i got after figuring out i got 14
Does anyone have any idea how Im supposed to go about solving this question?
square root of 14 is is 4
lol
Do you know the circle theorems required?
Have you heard of circle theorems?
You can find x using the cyclic quadrilateral one
then use the angle at the centre theorem
Ohhhh
That makes much more sense
But id need to know BAD and DCB for that
Wouldnt I?
What does the cyclic quadrilateral theorem say?
Yes
Welcome
can anyone help me with this, its not a test
A) is simple trigonometry, just scroll up and ive already explained how to do it
B) i actually suck at trigonometry so I couldnt tell you
im not sure ab this
I know how to do
Oh that
yeah
I forget how to do that
I think I can help
oh
can anyone help me with this
nintendo
thanks
wym
a^2+b^2=c^2 but wouldnt it be 100^2+b^2=130^2?
like what has been your attempt so far in getting the solution
not much ive been absent for the past few classes and im not sure where to start
yh
hyp²=adj²+opp²
that's what you use for a
do you know what side we're looking for here?
Still need help solving this?
so how would i solve for that
since you have the hypotenuse and the adjacent you just plug in the values for Pythagoras
then change the subject formula to find the opposite
since that's what we're looking for here
10²=5²+opp²
10²-5²=opp²
If you need help with part b lmk
ye i need help
They are just labels basically
Do you know how to use trigonometric ratios?
yo tiggle u tryna copy me?
Not quite. Remember Soh Cah Toa
Who are you imposter?
Stop twerkin' my square booty
Ok let me do some writing
D: Doodlebob
