#help-26
1 messages · Page 146 of 1
I've divided a figure one way but it wants it a specific way
so i get confused
So just do it the way I have it right now?
The way you have it now is perfectly legal, yes
ok thank you
If you're in a tyranical government
then they may ask you to comply with their way
calling yours wrong
do not listen to them, liberate yourself from the shackles of "my way" math
that's what my teacher tells us
can you just stay here for a lil longer just in case i get it wrong
Sure
ok thank you
So according to what I think
I did this right
and it equals 109.5
sq in
How'd you get 48?
OHHHH SHOOT
i didnt type in the answer yet tho
I just realized my mistake
it's supposed to be 36
ye
looks good to me now
ok
ok I got it right
I need one more and I'm done
but I need to make sure how I split the figure is legal
is this as legal as my birthdate
sure looks legal to me
ok
i put numbers in
sorry if they bad
but im on a laptop
and using my mouse makes it worse
so it's 104.5 sq cm right?
Looks good
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which question
and also:
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
for b, since the entire expression is equal to 0, you can just consider the numerator, and so x+5=0, and x=-5
for c take x common (dont cancel it out) and then factorize quad eqn
for d, tell me what method you use for solving inequalities?
for d i could do
and for e take LCM and simplify
(x+3)(x-3)/x+1 _> 0
can u help on c a lil more
okay
so yk wavy curve method
ive heard but not really
aha actually i also don't know wavy curve method, i just solve it with some diff method
and I cannot explain it unfortunately
dang
I suggest you to learn wavy curve method from yt or just ask your teacher
ill try from yt cause
this work ahs to be done by tomorrow
haha
its summer work for ap calc
uh
and product is 15
okay
tell me
product = -15
i meant my bad
NP
so we write the quad as:
3x²-15x+x-5
now we take 3 common
3x*
3x(x-5)+1(x-5)
(3x+1)(x-5)
now we keep it in original eqn which is:
x(3x+1)(x-5)=0
can you tell for what values of x, the eqn is satisfied?
how -1?
yea
is 5 right?
okay so x=0,-1/3 and 5
ez
now I go to sleep, it's 2:30 am here
ahah
b is really easy
okay
do it
ok
aha i trust you
i think it is
kk
<@&286206848099549185> can someone elaborate on d
im confused on the wavy curve method
not sure about the wavy curve method
but what you usually do when you have a situation like this:
f(x)/g(x) >= 0
Is analyze the sign of f(x) and g(x)
In this case you want to see when:
x^2 - 9 is positive, negative, or equal to 0
and when:
x+1 is positive, negative or equal to 0
so what we do is draw a tabel like this:
and ill complete for x^2 -9, and then you complete for x+1
okay
no worries, you should take a break, ill show you how to do it for x^2 - 9 and you can come back whenever you want and try for x+1
i just need to do it now tbh
i have to have it done by tomorrow so
oh
now you need to do the same for x+1, draw the lines where the function is equal to 0, and then see on the left and right side if its positive or negative
oh yea I use the same method
after doing that, complete the last line, note that the fraction will be positive if both the top and bottom are positive, or they are both negative, and if atleast one is negative than the fraction will be negative. If the denominator is 0, the fraction isnt defined so you will get a strict inequality, if the numerator is 0 the fraction is 0
@slow flower if you're too tired heres the solution:
you just need to see when its positive or equal to 0 since thats when the function is > or = to 0
but this is how you would go about solving these types of inequalities since you can never multiply by x unless you explicitly know its sign
@slow flower Has your question been resolved?
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A standard deck of cards contains 52 cards. There are four suits, (diamonds, spades, clubs, hearts), with 13 cards per suit. Given that a card chosen out of a standard deck is a diamond, what is the probability that it is a face card (king, queen, or jack)?
this is pretty simple stuff but the wording is throwing me a little
3/52 is right im 90 sure but there are 3 face cards per type of card, right?
idk anymore
Is it not 3/13
oh no
why would it be 3/52 
this is gonna be so embarassing let me read that again
You have a condition
probability of getting a diamond face card
Yeah
3 diamond face cards in a deck
reread it
it should probability of getting _ given _
what do you mean by this
i think he meant the condition is a card chosen out of a standard deck is a diamond
Let's isolate what we have - we know we pulled a diamond, which means there are 13 cards we could have. Out of these 13, 3 are face cards. Therefore, our answer should be 3/13
np, take care
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lol no problem
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the difference between these 2 are that small-sample should work for small n and large sample should work for n >= 30? I dont rlly understand the difference
because 2 slides after the small-sample CI I see this:
that means the t method will also work for large n?
oh im slow so the first one is for mu, sigma(unknown) and second is for mu, sigma(known)
now im only confused about this. it says (small sample) but here it says when sample size is larger than 40, 50 the t method is safe to use
so that means it can work for both large and small samples? 
t-distribution
Converges in distribution to the normal
So yes it works with large samples
so the sample size doesnt rlly matter? if it works for both small and large

also why is it named small-sample CI then
You can always use t
But it’s jsut more annoying to use
Than the normal
Because in t you have a degree of freedom parameter
And the pdf is uglier
oh wait im so dumb. so the z method works for larger samples and t method works for all of them. but for small sample sizes we have to use the t method thats why its called small-sample CI?
Ye
ye but easier to use z
Yes
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There are 12 people that have entered a gaming tournament with prizes for 1st place, 2nd place, and 3rd place. How many combinations of winners can there be?
12x11x10
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Hello all!
Yesterday I asked this question (photo) and was told to multiply by 4 and 8. Then I asked why specifically 4 and 8 and the kind helper replied with “Well, you have that the lengths of the larger solid are 2x the lengths of the smaller one, which means that the surface areas will be 2^2 larger, and volumes are 2^3 larger”
Okay. Makes sense. But what about this new question where the scale factor is 2:7? How can I know how many times bigger or smaller the objects are?
Surface area scales quadratically with respect to length, and volume scales cubicly with respect length
so you would have $SA = 28 \cdot (\frac{7}{2})^2$
shawn_xu
7 on top?
shawn_xu
Wait why is 7 on top
because the scaling factor is 2:7
and you are given the surface area and volume of the smaller solid
so the length of the smaller solid to the larger solid would be 2 to 7
and if you solve the ratio the length of the larger solid is $\frac{7}{2}$ the length of the smaller solid
shawn_xu
Ohh okay
If the scale factor was like 4:8 would I do 8/4 ?
But if it gave me the v and sa of the larger solid then I’d put 4/8?
yes
Oh okay
Thank you
Sorry to bother but I have one more question. For this one I picked 2 sides and put them as a fraction (8/12) and I got 2/3 = 2:3 but idk it’s wrong
well it's similar to the questions above
you have the the length of the big cake being $\frac{3}{2}$ the length of the small cake
shawn_xu
so the volume of the big cake is $(\frac{3}{2})^3$ the volume of the small cake
shawn_xu
How did you know to put it 3/2 and not 2/3
Bc they’re asking small to large?
And not large to small?
I’m just confused how you can tell
Or 8:27
@sour egret Has your question been resolved?
Since you need ratio of volumes
All I think is to be done is multiply all sides
And then take the ratios
@sour egret Has your question been resolved?
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can someone explain naive bayes classifier in extremely intuitive terms?
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I can't seem to do this
btw it is 30 degrees not 630
,rotate
thx
@livid garden Has your question been resolved?
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I am stuck on this one.
Let $\vec{L} = \begin{bmatrix} 1\ -6 \ -2\ \end{bmatrix}$. $proj_L(\vec{v}) = \vec{v}(\frac{\vec{v}\cdot\vec{L}}{\vec{v}\cdot\vec{v}})$
This is what I've established so far.
Narutoes
I got the dot product fraction to be -6/23
But it's saying it's wrong.
The software is saying the answer is $\begin{bmatrix} -\frac{42}{41}\ \frac{252}{41}\ \frac{84}{41} \end{bmatrix}$ and I have no idea where those numbers came from.
Narutoes
@steep ibex Has your question been resolved?
shouldn't it be v (v dot L) / (L dot L)?
How so?
i'm not positive but iirc that's the formula
I thought we were projecting v onto L
Lemme try that and see what happens.
I missed this day of class because I was in the hospital for 5 hours.
So what I have is notes from the guy next to me.
u spans the space that you're projecting onto, v is the vector you're projecting
so in your case it should be <v, L> / <L, L> v
So it would be -42/41? That fits more with what the problem is saying
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i need help with homework
Yo
!15m
Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.
i got a math question that needs help
the topic is called plotting linear graphs
and the question is, plot 2 points and use them to draw a linear graph
the equation is y=2x-1
idk how to do this one
i need someone to tell me what i need to do
i dont even know the vaule of x
at the top
it says x vaules -3, -2, -1, 0, 1, 2, 3
ill send the pdf file of what im talking about
They ask you to plot some points and link them. You need to find a y-value at a specific x-value
For example, what is the value of y when x=0?
here is my lesson im doing
you can take a look if you want
my homework is the examples
the first example
Yo
!filetype
I'm back
Please post images (such as PNGs or JPGs) of the question rather than other filetypes such as PDFs which have to be downloaded. Non-image downloads can potentially contain viruses or other security risks.
!fishy
I am saying that don't send links which may seem fishy
Send a SS or elaborate
What u want to ask
Okok
they just want you to plot that curve with 2 points
It is given that it is a linear graph
ok
to plot it you just have to consider any points
do you have to like make a table with x and y with the equation or not
yup
that's what you have to do
ok
But that fact is that you are just allowed to get two points
tho my next problem is finding the vaule of x
with that equation
y=2x-1
would x be 1
or is y equal to 1
you just have to take any values that you like
for example take x=something and then solve for y
and you'll get a point
ok
same for other point
so how do i solve my equation to find what i need
You're not supposed to solve for the equation
you're just given one
oh
you have to plot it
follow this procedure
or you can do vice versa by taking y=something and then find corresponding x value to get the point
yup
then ill have to make a linear graph which i have already done with 4 equal quadrants and with y and x axis
all i need to do is plot 2 points of the y=2x-1
ok
i think i can do this
and do not forget to join those 2 points for the actual curve
ok
hmmm
so what is my first dot going to be
where i meant
i dont know the decimals on which one
there negative and positive numbers on equal sides of the quadrants
huh?
what are you doing with quadrants?
no because a linear graph has 4 quadrants
what is the highest number should be for my linear graph
@rigid cloak you here?
Yo
bro you don't have to consider any maxima/minima for this curve
Bro
idk what you mean by maxima and minima
Plot the straight line
straight?
77 told me it was curved
ok i got it ow
now
i got the 2 plots on my cartesian plane
thx for the help
but now i got another homework
its called features of linear graphs
bro a curve literally could be any straight line/point or anything else
this includes gradients
ill get a ss of my last homework i need help with
heres my first part of my last homework
it says calculate the gradients of the lines
which is confusing for me
my homework is a and b and d
explain what a gradient is pls
hello?
<@&286206848099549185>
ok
so my first gradient should first have to be a calculation of a rise and run?
ok
so all i need to do is find the rise and run
hey i have that formula in my lesson thing
so its the substitution thing
ok
ok
oh
my rise and run for c was 0 being my rise and 5.1 for my run
oh wow
thats cool
i never expected math teachers to use discord if im being totally honest
anyways
my last questio is now b
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@mild tapir Has your question been resolved?
<@&268886789983436800>
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how do u do part b?
do u start by doing this?
I feel like they meant tan^-1 2x
But it's solvable either way
Nah I'd win 🗣️ 🔥
The hence bit tho is what I'm confused about
Stop disrupting help channels with nonsense, please.
Idk what keygen funk is
I'm sry got carried away
nope
You won't be able to use the previous identity if you set alpha = tan^-1 x because then beta = tan^-1 2x which won't work with your equation in b
Which is why I'm half certain there's a typo in that question
Anyway, you can still solve it with the exact same way you derived the equation in part a
U learn the formula you will be able to solve then
Wait wdym
You used compound angle formula to show the equation in part a right?
So after I do that, I expand LHS and it will get me the answer?
You'll have to solve the equation you get from doing that
I got x=1/3 and the answer is x=1/2
But this is for the case when xy<1 tho
we have to know about xy to apply arctan x+arctan y formula
yea
Okay, so it might be a typo after all
I feel this is the problem
this is good approach
Oh
Replace the 2 with 2x
Ohok
so like this?
That is what I mean but I solved it and didn't get a 1/2 either
Oh
I think I get how do it, just the typo is messing the answer up
Thanks a lot :)
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Np
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can I have help with part b
what have you got so far
nothing, all i got is the costheta = uv/|u||v|
and idk what to do with it
Isolate u.v
and square it
:/
wait
can i do this, make u and v into magnitude. by squaring both of them and then cause |u||v| is hyp, its larger than the other one
There is a much simpler way with the calculation
ah but then ig it cant be equal to
what do i do with the costheta then
Just write (u.v)² = ...
(u.v)^2=|u|^2|v|^2 cos^2theta
you got it you know
What does the question ask you?
?
it asks for bounds
no
sorry
asks for whatever it says there im not bothered to write it
i dont care about the equality part
Closed by @deft holly
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and btw, (u.v)² = | u | ² * |v| ²
when theta = 0 or 180
but i think you guessed it
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Is {(-3/4), (-1/2), (1/2), (3/4)} function or mere relation?
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{(1/2,5),(-1/2,6),(3/4,7),(-3/4,8)} is it a function or mere relation
Is it okay for x values to repeat if the other one is a negative?
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If im not mistaken the only vertical tangent is on the far left
So im not really sure what exactly we do
We need the derivative of something to get the slope of the tangent
And I think we set something equal to 0 cause the slope of the tangent is 0
But I dont know specifically the steps
Im also thinking maybe we ignore y(t) and only do something with x(t)? Because we dont care about the y axis or something? Really not sure
<@&286206848099549185>
@shell orbit Has your question been resolved?
??
??
@shell orbit
Vertical tangent line
That like slope is 90
find dy/dx as (dy/dt)/(dx/dt)
,w d/dt 2t^4-t^2
,w d/dt t^3-3t
So dy/dx=
3(t^2-1)/(8t^3-2t)
Now we need dy/dx=tan90
That is not defined
Only possible when 8t^3-2t becomes 0
,w 8t^3-2t=0
Wait sry to interrupt I have a lot of questions
Was I right about this? That the red line is the vertical tangent to both points?
We need the derivative of something to get the slope of the tangent
And I think we set something equal to 0 cause the slope of the tangent is 0
Im also thinking maybe we ignore y(t) and only do something with x(t)? Because we dont care about the y axis or something? Really not sure
And was I right about these?
Why do we want tan(90)?
The three points we get for
Three values of t
Fr
No
Slope of tangent is undefined
Slope is the tan of angle made with+ve horizontal axis
Y axis makes angle 90 degree
Slope is tan(theta)
Like dy/dx=tant
If line is vertical
t=90
And tan(90)is undefined
That is slope is also undefined
The middle point I can clearly see is at (0, 0), can I just say 'I see from the graph that its 0, 0' or do I have to use time proving it? I dont have a lot of time in my exam...
See
U have to prove
Ike see when I set the denominator
8t^3-2t=0
I get t=0
As a solution for which slope is undefined
And so I get x=0 and y=0 by putting
Moreover depends on your exam
If MCQ or choice baswd
Mark directly
Else show
The working
Hmm ok
Thats easy to prove at least
I think I know how to solve the rest tho
I just sub in 1/2 for t
And -1/2
And get the coordinates
easy enough
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Can u explain me why cot theta has values
When it is 0
Tan theta also becomes 0
bruh
nahh
Then shouldn't it be pi and 2 pi?
you know the tangent graph?
Tan theta=0 and so theta=0
Like as he mentioned in above question? Or typically?
Okay and?
i just wanna talk about asymptotes
Where does tangent comes from?
Asymptotes well like the specific tan graph
So I will take values of 1st and 3rd quadrants only
But why the heck theta is half pi and 3/2 pi
I'm confused
First
Share the question
Like the question of the answer u mentioned
Yo
sup
Here is the question
Blud first check ur answer
Be it's zero...
bro really said 1/0 is 0
Good question 😢 TT
Then how am I supposed to solve this
when tanthta is infinity
Tan theta is infinity
Please I am ashamed
1/infinity is 0
weve all done something like this before lmao
Seems like it's new for me, never done something like this before
OK, I get this but later what happen
Like how did the solution comes 1/2 pi?
Yes
Okay then...and asymptotes lines are on x= 1/2 pi, 3/2pi like this?
yea
Can u explain a little bit further?
on what exactly
If I want my answer while doing on the quadrants?
i mean
what im saying is just a theory thing
this is also just exact values of cotangent
its not defined
it approaches infinity
Lol
Doubt solved?
Ig kind of
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Hmm
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\left.f(x,y)=\begin{cases}\frac{2x|y|}{\sqrt{x^2+y^2}}&(x,y)\neq(0,0),\0&(x,y)=(0,0).\end{cases}\right.
riyobi
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does f_x(0,0) = 0 = f_y(0,0)?
for all values of 0 it is 0 otherwise it is the top function
@strong sable Has your question been resolved?
I only want to know this so why do i need the differentiable thing
Well you wanna know if there is a derivative at (0,0) so the approach I sent above would be to see if it is differentiable at (0,0). If it is differentiable in (0,0) then it has a derivative in (0,0)
why cannot i just directly check if the drivatives exist? why do i have to check it by checking if it's differentiable?
Well you can also calculate the partials and then see if f_x and f_y exist at (0,0)
so is this correct?
okk, thank you, i'll let this channel open to see if others can confirm this maybe
Well in general you could have partials exist but not differentiability
Yeah thats correct, since you seemed to only ask about the partials
?
theyre asking about the partial derivates, whatever just the word "derivative" means in this case
how can the partial derivative exist in one point but at the same time you say it's not differentiable there?
By the definitions
theres some classic examples of it
theres even some bizarre ones
However what you can say is that if your partials are continuous, then yes we certainly have differentiability
Maybe theyre talking about some other notion of the word "derivative"?
and not partials in this case
idk if i should ping them but anyway
if they dont bother sure
i mean it's the same situation with |x|
they said that differentiable and derivative exists is synonymous
how is it the same with |x|?
but that would go against what you sent
well there exists a derivative by calculation
but it's not differentiable in x = 0
Uh, how exactly?
x/|x|
and what did i say?
yeah but that's different in this case
it's differentiable also aprt from x=0, in the one variable case it doesn't make sense to talk about partials
i wasn't talking about partials
yeah so how is this the same in that case??
it's an analogy
Uh how?
in both cases you are asking if it's differntiable in some point
It would be an anaolgy if you had some kind of notion of "derivative" which existed at x=0
one case is in one dimensional other in two dimensional
well you have x/|x| but the right and left hand side limit are not equal
for the partials we have a limit at particular point, meanwhile for differentiability this does not work for the same point
so i dont see how this is an analogy
in the one variable case the the notion of derivative and differentiability are the same thing since their def. are the same, but for higher dim. we have a notion of a partial derivatives, and then differentiability again; but this time their def. are different
and maybe snow is using the word "derivative" differently here, but for partials this is most definitely not true unless im missing some context from ur convo with them
i don't understand why it would be different in higher dimension, the partials derivatives are also just a limit that comes from the definition in one-dimensional case
have u checked the definitions?
you can sorta see how they reduce to the same thing once we're working in one variable
also what's funny is that this can be a wording thing too, in Sweden we dont ever use the word differentiability until we talk about the def. in higher dim. and that was precisely to avoid confusion
it's not funny cause i am getting crazy lately and feel my whole concepts are based on trash
it's not funny when you are entering your 5th semester knowing shit
I think it's funny in the sense that maybe it's the way the words are badly used is what is causing the confusion
i.e not your fault but the way theyve been taught
like we would use the word "derivable" if i try and translate it for one variable and i thought it was dumb right up until we started using the "right" word in higher dim. and it clicked a bit faster that way imo
Well we defined in one-dimensional case back then that a function f is differentiable in some x0 in D(f) if 1. the left hand side limit equals the right hand limit of the derivative limit definition with that "h" and 2. f is continuous in x0
notice how that just becomes the same thing if we try and reduce the dim for the partials def. aswell
in reality i think it's sorta weird to talk about partials in one variable, but i would say we are basically treating it as the derivative in that case
for the 2-dimensional case we didn't even bother to define differentiability other then what partials are and how you calculate them. We only got shown how to investigate continuity
Huh thats weird
Also btw we should prob move this convo away from this help channel
@strong sable i hope u got the help needed btw
no this is a related topic, i can learn from it also
Thank you btw
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I feel like the function is supposed to have a ^2 in it somewhere but I’m not exactly sure where
the 3 on the left before the ()s isnt correct, youll need to check that
remember that f(0) should be -3
the function doesnt have a ^2 in it because all of the roots cross through the x-axis like lines, so theyre ^1
if a graph as x turning points, wouldn’t have a degree that’s is essentially x + 1 ?
that’s how I got three, for context
if you can see the turning points, then you can see the roots
when you add up the degrees of each root you still get 3
something like this is degree 6
the root on the right is degree 1, it looks like a line
the root near the right is degree 2, it looks like a parabola
the root on the left is degree 3, it looks like a cubic
the 6 is from 1 + 2 + 3
however the graph itself only has up to 4 turning points
so seeing the roots directly will tell you the degree, the turning point idea only sometimes works
np
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Part C
c1 is (y + 1)^2 + (x + 0)^2 = 16
c2 is (y - 5)^2 + (x - 8)^2 = 36
So for the question I know we need to use the formula (ax + by + c)/sqrt(a^2 + b^2) = length of radius of circle c2
Im not really sure what to do with it though, or how to get the unknowns
@shell orbit Has your question been resolved?
<@&286206848099549185>
yoyo
Wym sry?
Can u send me a white page
A online photo
Leave it ok
Imma explain
Verbally
@shell orbit
U know end points ?
I mean diametric form oc circle?
See BC is a diameter
So B and C become end points of diameter of
C2
Now the diametric end points form says
A circle with end points of diameter (x1,y1) and (x2,y2) can be written as
(x-x1)(x-x2)+(y-y1)(y-y2)=0
Now solve and tell me c2
@shell orbit
Take your time read understand and tell me the equation of c2
ye I need to reread a few times
Its not in this form right?
Its wrong? 👀
Yes
(x-2)(x-14)+(y-5)(y-5)=0
See u know when do circles touch
So not really sure
?
Two circles touch when distance b/w their centres is R1+R2
In this case they touch externally
For the case in which 1st circle is inside 2nd circle
And touches internally
It's different
(16/5, 7/5)
What
Thats where they touch
Yeye im stuck on this
See
c1 is (y + 1)^2 + (x + 0)^2 = 16
c2 is (y - 5)^2 + (x - 8)^2 = 36
So for the question I know we need to use the formula (ax + by - c)/sqrt(a^2 + b^2) = length of radius of circle c2
Im not really sure what to do with it though, or how to get the unknowns
Do u know
Ah
I forgot the form
Ula
Maybe I need to derive it
Wait lemme derive
See
Consider a circle
And we have a point outside it
We draw two Tangents from it to the circpe
Circle
Yes
Good
Now see
I don't remember much
But see
If the lines touch
The circle
We can get the slope of them
By doing derivative as they tangent
@shell orbit
We know one point on both the lines
So we can calculate their slope using that
Then we equate the slopes using both forms
To get x and y
That is where the lines touch circle
What about my method? Using (ax + by - c)/sqrt(a^2 + b^2) = length of radius of circle c2
I forgot so I am doing this if your have better approach then good
It doesnt use derivatives



