#precalculus
1 messages · Page 51 of 1
Sure but my point is at some point we have to define arbitrary stuff to avoid ambiguity
sure
in terms of mathematical notation and communication, absolutely
the issue here is your problem is about understanding how transformations work, right?
it's not that I'll memorize some distorted mnemonic to deal with the operations
I just wondered why it is the way it is
I'd say it's about the undercurrents of the convention
What do you mean
I wouldn't memorise this order
cause it's not even true that you have to follow that order to get it right
Yup I've realized that translations and transformations are inherently interchangeable
cool
there are operations for which order doesn't matter and those for which it does matter
which is why division sucks
Hello can someone help me on describing the end behavior and any ezcluded values with limit notation in dms pls
do you have a public question 👀
Domain and range is easy but im confused on “describing the end behavior and any excluded values with limit notation”
^
did you come up with domain restrictions?
two of them :>
Yes
do you know limits?
Domain is all reals and x cant equal plus/minus 2 and y is all reals
yeah
Yea i know basic limits and stuff but i forgot more complex since this a 3 way thingy graph
do you know the limit approaching these domain restrictions/excluded values of x?
Yes
Plus or minus 2
well you'd look at the limit as x approaches -2 or 2 right?
4
approaching 2, approaching -2, approaching infinity, approaching -infinity
those are your limits, right?
But what about middle
what about the middle?
Yes
is there a discontinuity there XD
is 0 an excluded value?
then why are you looking at the behavoir approaching 0?
Idk tbh
it tells you to look at end behavior (as x approaches +-infinity) and excluded values (as x approaches +-2)
so you'd have four limits
Mot end behvauor of all only excluded values sections?
with the same instructions, the function would have to have four discontinuities like this instead of two ^
end behavior just means approaching infinity or -infinity
thats seperate from the excluded values
the end behavior is 2 limits
always
but in this case there are two excluded values and one limit for each value
what is the other problem?
X +8x^6 -12x^3
oh LOL
whats the highest power term in the limit?
or just the highest power in general lol
6
yeah
In the denominator
divide the numerator and denominator by x^6
so like
[(13x^3 - 1502x^2)/x^6]/[(x+8x^6 - 12x^3)/x^6]
you see what i mean?
i cant read 💀
same answer in fact 💀
I have that now
Wait one sec
so the limit should become this
Ok i havd that
Smaller
right its approaching 0
Yes
yea
So equal 0
so the limit is just 0
🤯
fun fact: you can just take the term with the highest power in the numerator, and the term with the highest power in the denominator, and take the limit of the highest power in numerator divided by the highest power indenominator
so like, here it would be lim x->infinity 63x^3/8x^6 = lim x->infinity 63/8x^3 = 0 still
there are rules regarding limits of infinity in the same way that there are rules when finding asymptotes of a rational function
because all the other terms are going to 0
yeah...?
what about it 💀
oh no, i was just saying because i saw the question and thought of a faster way of doing it
oh you probably mean that ^
or something liek it lol
yeah
Omg
I did not know this
well its a faster way but hopefully you see why it works
it only works with infinite limits tho
I am catching up on 5 pre calc lessons and 2 bc lessons
(or approaching -infinity)
mind if I help?
Yea sure
So i have y=3x/ absolute value phrase x-1
And i have to find the domain and range of the function describe the end behavior and any excluded x values with limit notation
the absolute value of x-1 is equal to two functions:
-(x-1) if x < 1 and (x-1) if x> 1
the domain is, of course, how far to the left and how far to the right it can go
it has a vertical asymptote at x= 1 as well
And horizontal of 3 ??
positive and negative 3
that’s why the -(x-1) is important in this case
But than what about this graph
Thats the graphbof the equation
How does the horizontal work here
horizontal asymptotes are positive and negative 3
But how? Than
Is it allowed to go through?
-(x-1) = 0
becomes x - 1 = 0
x = 1
x-1 = 0
x=1
you’re also looking for the domain and range
the domain is how far left to right the function can go
the range is how low to high the function can go
So x all real and y > -3
let me see:
domain: (-infinity to 1) U (1 to infinity)
i’m not sure about range though
Hole ok
So the next part is describe the end behavior and any excluded X values with limit notation
oh i see
we can say that the limit of the function as it approaches 1 is infinity
And thats it
Oh ok wow thats weird
What about the other 2
As it aproaches infinity y is infinity and is it aproaches negative infinity y is negative infinity?
limit as the function approaches +- infinity is -3 and 3
Oh my god this is making sense
I know i got it wrong originally but still
Tha k you
i’ll give you proof if you want to look into detail
or i can explain it to you
whichever option
Wdym
as to why the limits approach infinity make sense
so, this is where the rules of a rational function come into play regarding limits approaching infinity
one of the rules is that if the power of the numerator is equal to the power of the denominator, then the horizontal asymptotes is equal to the coefficient of the numerator divided by the coefficient of the denominator
here, with the function that we were solving, the powers of both the numerator and denominator were equal
that’s how we got 3 and -3
so, with limits of infinity, the rule i mentioned still applies since the powers of both the numerator and denominator are the same
Oh ok yea and what gets the denominator to 0 is vertical asympte? But how does slant higher top than bottom or higher bottom than top power wise
i do need a little clarification on what you’re trying to ask me with this question
also, yes, the vertical asymptote is obtained when you set the denominator of the function equal to zero
How would i get the f(x) nunber of the limit if it is set to inifinity but the either the numerator power is higher than the denominator or vice versa
Hey guys, so Im learning functioms amd polynomials in my precalc class and I am so lost on the graphimg padt
So, I thought since the degree was positive, the graph falls to the left and since the leading coefficient was positive, it rises to the right
I failed a question bc I got the "a" part wrong
Could anyone help me explain how to understand the "finding the end behavior" better?
oh when the power of numerator is greater than or less than the power of the denominator?
greater than: the horizontal asymptote does not exist
less than: the horizontal asymptote is 0
Yes
Oh ok
I see thank yiu fro all the help
also, this means that limit approaching infinity is infinite for “greater than” and 0 for “less than”
Is anyone gon help me... halp
i was reading your question and i’m here to help
i just needed to help Vibez with the final part of their question
Thank you, thank you thank you SMMMMM
Ok this ia gon take me an hour to despipher ill brb 😭
If u can help explain in simpler terms id appreciate
@winged peak i do want to add with the function behavior:
for example, when they tell you as x approaches infinity -> f(x) approaches infinity, it’s telling you to read from left and right or right to left
Just in advance, I have a slight lesrning disability so im kinda slow 😭
we’ll still help regardless
Thank you, Im new to my university and i have no intention of fucking around over here 😭
If even highest degree or combined degree they go same direction if lead coefficient is greater than 0 than it goes up both sides if less than 0 they go down both sides
If odd highest or combined degree they go opposite side
If greater than it goes down than up if less than 0 it goes up than down
Alr I uave to do a DIFFERENT question thats not the one i showed on paper, but ill ask you for help later. Its ok if u dont anseer immediately or jave othee things
Draw your arrows than your bounces sqiuggles and straights if your graphing
Yes im graphing on a computer i just showed my work on paper
Am i right @gritty totem ?
yeah
and you can factor the function to see where the zeros are located and use the information to sketch the graph after
Yep but if its factored out dont take the highest degree there you need to add them up including if there is a x without a clearly defined power its 1 if not another
yep
Can i dm you like monday or something since i got a test Wednesday
sure
and what’s the test about?
The bc 1.1 is easy its just areas of rectangles for the underside of a quadratic thingy
oh ok
hi, im new can anyone pls explain what calculus is. I really would like to learn
and teach me the basics and stuff
calculus is the study of rate of change and it’s split into two categories: differential and integral calculus
differential calculus is finding the rate of change of a function such as derivatives (which is the slope of a function)
he doesnt know algebra either 😔
who? thecoffeedrink?
oh i see
i don’t mind someone being curious to calculus at all, but if they’re wondering what algebra is, then algebraic work has to be covered first
yeah xD
i'm not sure if the explanation would work without knowing algebra XD
could just say "study of changing things and....infinite things :>"
😂
oh i see
Ayo could u fact check this
Nvm it was right I was being delusional
This is correct
Bro, the website I do my hw on is called aleks
and if I get 1 problem wrong, I'm assigned more questions
And it's like I'm traumitized at this point and in tears
That name hasn’t popped up in my mind in years
This website is fucking ass like it charges me money to do my damn hw and Ion even use the damn e book
SLAYYY MEE TOOO
I have multivariable calculus and intro to proofs - which is why I have experience with precalculus
i have experience with precalculus but i never took it 
and my homework is mainly on paper; some is through technology but it’s for a “quick check” from the concept i read for intro to proofs
it still technically counts though... 
Wait
this channel banns the topic regarding ... " i - q"
Bc I was literally tryna compliment u omg 😭
what exactly?
i technically still have experience even though i didnt take it
i mean like idk if it can be called 'experience' but
:l
oh i see
💀
but hey, there’s nothing wrong with self-teaching yourself a subject
they do?
Yeah
I just responded to u "Wow, ur i - q must be up there w albert" and the server banned it due to irrational arguments over it idk
try it 
Honestly Ig for a server w 200k users, sounds reasonable
i guess as well
Idk how long u been here but has this disc chat had any chaotic moments
just joined today so i don’t have much of a clue
usually pretty chill 💀
Thank god. Hope yall dont mind my username I would change it but this server doesnt allow LMFAO
Oh, and ur one of the smart ones too! Please verify if this is correct. If I get this right, this is the last question I have to do.
😂
Yep, this one’s right
Alr tysm for clarifying bestie. Transitioning to college has been like, kinda wild if I'm being honest. I love it, but it's quite difficult to adjust here and there. The math hw I was just doing was only like, prep, which was tedious asf.
And the weird part is, the math prep usually has nothing to do w the exams, or lecture. Like I barely passed my first exam which is giving me hella anxiety. 😭
It's nice to meet u tho! Hope to talk to u more < 3
i would say the same as well in terms of transitioning because i have a more lighter schedule for classes whose difficulty increases as the semester passes.
and with math, the more practice you do, the better; i do believe by your next semester, you take calculus - i could be wrong but i’m just predicting in the case of it all
likewise
Yeah that's correct im moving to.. actual calculus? idk if I'm dying here, it's probably bc of the professor smfh
Do u dorm ???
no, my home is near my university
ANYWAYS I GTG TO WALMART AND BUY TOILET PAPER BYEEEE
Oh, slayyyy. I dorm bc I can't drive
toilet paper is such a life saver ngl
oh i see
Fr bc all I eat in college all day is Panda Express
yum :>
Bros name 
😭 dude why tf did i read this
Wait
sub 1/x = t
af(bx-c)+d vertically stretches f by a, horizontally stretches f by b, horizontally translates f by c, and vertically translates f by d
Obv each of those can be done individually too or in whatever combinations but I just stuck it all in one place for conciseness
So for these to be correct you’d have to stick the vertical translation outside of the argument of f
Cause f(x) + k vertically translates f by k
For the factoring thing it depends, you just want to be able to express it in a form where you can extract this info relative to some function f
Can someone check if these are correct
g(x)=2x^2 -6x+4
h(x)=-2x^2 +10x -12
j(x)=3x^2 -12x +9
,w polynomial through (-3, 40), (1, 0), (2, 0)
,w polynomial through (-3, 0), (1, 8), (2, 0)
,w polynomial through (-3, 0), (1, 0), (2, 15)
check your answers yourself
only g(x) is correct
do you have reviewer on pre cal guys?
Here is a set of notes used by Paul Dawkins to teach his Algebra course at Lamar University. Included area a review of exponents, radicals, polynomials as well as indepth discussions of solving equations (linear, quadratic, absolute value, exponential, logarithm) and inqualities (polynomial, rational, absolute value), functions (definition, not...
i dont understand how to find this
Nvm
I didnt know if the - - 3 would make it positive when factoring now i jnow
I sent a video in your help channel and you deleted your msg, you're weird for that
sorry if it's wrong channel but can u guys help me this
Given sequence a1= 1, a1<a2<...<ak such that these positive integers < m and coprime with m. Prove that if the sequence a1,a2,...am is an arithmetic progression with at least 3 numbers, so m will be a prime or an exponential of 2
hello guys
Im new here can anyone suggest me or guide me where i should start from.
Im in High School
you might wanna check out Professor Leonard
on YouTube
thanks for the suggestion
anything else would u like to suggst for me
maybe start
😭
I am nerd
Precalculus test was easier than I expected, I am definitely improving.
Hello everyone I wanted to start calculus but I lack many concepts I have studied math till 10th grade Real Numbers
Polynomials
Pair of Linear Equations in Two Variables
Quadratic Equations
Arithmetic Progressions
Triangles
Coordinate Geometry
Introduction to Trigonometry
Some Applications of Trigonometry Circles
Constructions
Areas Related to Circles
Surface Areas and Volumes Statistics
Probability. So I wanted to know what else do I need to cover
can anyone help
Yes here.
someone recommend me to cover functions, integration, differntiality,limits and continuity
is it enough?
.
Professor Leonard
I know but
Yes. Enough to ability.
OK. high school
ya what about you?
I graduated from college.
Your age?
17
what major?
How do I proceed to prove this?
,rccw
Hey there! can someone explain me the difference between the slope and the rate of change? I understand them as the same, am I correct?
yeah, they're the same
And why they got different name?
why do you call them differently you mean?
💀
that was supposed to be a joke
anyways one thing can have multiple names, its how english works ☠️
I meaned, why In my book it has like 2 different terms for the same stuff
im not native english :/
"slope" is an interpretation of the derivative driven by the graph of a function, whereas "rate of change" is driven by interpreting a function as modeling a physical quantity
no
😔
unlucky
😭
Can someone help me on piece wise functions they are easy I just dont grt this problem 😐
whats the problem
Number 3
One of them is dne I think its the first but idk why
have you tried graphing it? it might help with understanding whats going on
I have not but on my test there wont be enough time he said
but for (a) you're gonna wanna look at the graph approaching 2 from the right and from the left
well you see that at x=2 the graph changes elementary functions, right?
because its -x^2 + 5 for x<2 (on the left side of x=2) and 4x for 2<=x<4 (on the right side of x=2 including x=2)
so you're going to want to know lim -> 2- (-x^2 + 5) and lim x->2+ (4x)
if they evaluate to the same thing, then the limit is what they both evaluate to
if they evaluate to different things, the limit does not exist
am i making sense or nah 💀
…
💀
you might want to graph it this time just for a bit of visual representation
yeah
well first of all, as x approaches 2 do you see graphically that the limit doesn't exist?
like both sides approach different things
lim x-> 2- f(x) is not equal to lim x-> 2+ f(x) right
Isnt it becuase 1 value having more than 1 y value
without graphing it
How
do you know about one sided limits?
Yes
so lets say you're approaching f(x) from the left
lim x-> 2- f(x)
since you're looking at x values less than 2, which part of the piecewise function can you use?
remember the function is -x^2 + 5 if x<2, and 4x if 2<= x < 4
yeah so you're gonna use the function for x<2 right
so as x approaches 2 from the left, lim x->2- (-x^2 + 5) = the value you're approaching from the left
make sense?
Wait are you literally subtracting like this or a dash
lim x-> 2-
the - after 2 means its approaching 2 from the left
lim x-> 2+ would mean approaching 2 from the right
i shoulda explained that before 💀
Yea i know that part
When i look at it
Just dont know how to see this qithout a graoh just mind
🧠
like you can just think of some arbitrary graph but you only care about the graph for x<2
Ok
then approaching from the right, it should be the same value if the limit exists, right?
Yes
so lim x->2+ f(x) is the limit of f(x) as x approaches 2 from the right
which part of f(x) do you use?
you're only going to realistically use the values to the right of 2 that are close to 2
Yes
remember f(x) = {(-x^2 + 5) if x<2, 4x if 2<=x<4, and x^2 if 4<= x
if you're approaching 2 from the right but you only care about values close to 2, which of these do you use?
Only option is 2<_ x <4
right
so you're going to use the 4x part of the function
so lim x->2+ f(x) = lim x-> 2+ (4x) = the value of the limit as f(x) approaches 2 from the right
right?
🤣
the one sided limits aren't equal yeah
Ok i see
basically you have to determine from which way you're approaching, and use the appropriate part of the piecewise function. if the limits from both sides both evaluate to the same number, then the entire limit is that number. But if the limits from both sides evaluate to different numbers, the limit doesn't exist
😂
How do i know thag my line parobola thingys are going thr same direction if its like this
i guess you could take the limit
or just make a table of values as x approaches your discontinuities 💀
But is there not a way of just knowing that the graph will both be up vs being on opposite axes like 1 and 3 or 2 and 4
you could take the derivative and see if its increasing or decreasing on the intervals 😁
but i don't know of an easy way to know, maybe there is an I just don't know it tho
🤷♂️
Oh ok thanks tho
To advanced for me 😓
i'd just plug in values to see xD
hi im in Gr 12 in pre calc with a mark of 64, its because of my first test. and right now im doing polynomial functions in pre calc. i know how it works but the word problems, applying polynomial problems in real life is a big challenge for me so i beg that someone give me a lengthy advice and some support please and thanks
do you have a sample problem that you struggle with so we can see the type of problem?
Any single guys my age group plz dm me I want a bf to show my friends in school 😭
Rules :
17 or under
@wanton parcel Please don't use this server for that kind of stuff.
Hii I'm taken
worst year to be a minor
Can my birthday come already 😭
I feel threatened
I studied for the wrong thing on the no calculator part on the test 
Hello :) can someone explain to me how this works
(I also do not know what this is called)
$x^{ab}-1=(x^a-1)(x^{a(b-1)}+x^{a(b-2)}+...+x^a+1)$
Minute
I know its related to (x-1) always being a factor of (x^n-1) for any natural number n but i dont get how you derive that from this
also lmk if there was a better channel to pose this question in
wow duh thank you idk why this didnt hit me
do you know what that theorems called
Hmm idk
It's kind of related to the geometric series formula
And cyclotomic polynomials
ah thank you this is good reading :)
@safe blaze apparently its the difference of powers identity with b=0 1 :P
i think this or something related was mentioned in the advanced algebra channel
yesterday 5pm aest
Yo
Yo
Yo
Yo
Yo
$plot (sinx)$
Progno
,w plot sinx
how do we solve question 12?
Don't just give an answer
yes but, how did you get it?
i like to check my answer first
do you the sign of each trig function in each quadrant?
@quasi elbow
i do
also do you know what happens when you add $n\pi$ or $\frac{(2n+1)\pi}{2}$ to the argument of trig functions
Black_Gold
??
where were you stuck??
Please see below. We already know that if a,band c are in G.P., we have b/a=c/b or b^2=ac Now let us work out for other two relations When a,b and c are in A.P., we have b-a=c-b=d where d is common difference. Then we can write b^2-ac as = (a+c)^2/4-ac = (a^2+c^2+2ac-4ac)/4 = (a^2+c^2-2ac)/4 = (a-c)^2/4 As (a-c)^2/4 is always positive b^2-ac>0 i...
Can anyone explain this last part
What if the product of ac is negative?
can someone please explain this question to me? in this, we have to find the minimum and the maximum value of the given expression
You basically have a quadratic function and you wanna find the vertex form of it
since it's open upwards, it will tell you the minimum value is 3/4
in order to find the maximum we need to consider now the vertex form expression
sin²(theta) is bounded between 0 and 1
bacc the sigma😔🤞
how are we supposed to think of the process though, when we come across such questions?
if that makes sense
<@&268886789983436800> any moderators who wants a [ this person has been posting on here frequently asking for a dating partner ]
well here if you look at the terms you notice it's a quadratic in disguise
so might as well complete the square to get the vertex form etc
if it were instead of sin(x)^4 it was sin(x)^3 then it would be a bit more difficult
got it, thank you.
@exotic barn Können Sie mir bitte mit Wahrscheinlichkeiten helfen?
what is happening here
where specifically ?
okay
so
first
this part
for some reason i feel like this is wrong
cause pi equals 3.14
but
here they are taking pi as in radians
which equals 180degress
degrees
ah
thats the reason they said this
eh
i am still very confused
yeah that's wrong, of course pi isn't exactly equal to 3.14
but yeah sin of 1 degree is less than sin of 1 radian
sin of 1 degree is tiny
using the approximation $\sin x \approx x$ in radians
higher's secret twin brother
,calc pi/180
Result:
0.017453292519943
,calc sin(pi/180)
Result:
0.017452406437284
there you go, they're very close
so the graph shows you that sin is increasing in 0 < x < pi/2
and decreasing in pi/2 < x < pi
they drew a lot of lines yes
for instance, because 3 < pi, 1 < pi/3 and so sin(1) < sin(pi/3)
also sin has symmetry, so sin(pi - x) = sin(x)
so that is why sin(pi - 2pi/3) = sin(pi/3) = sin(2pi/3)
it is a lot of info yes
i had an eight-hour study session so nothing is making sense to me anymore
i will get back to it later
but thank you
np!
multiply by x-6
how does that make it 5x+19 though? shouldn't it be like x^2 -6x + 5x - 30 +4x - 24? thats what it is if you multiply x-6 with the denominator
yw
Well boys I'm cooked I'm way in over my head and there is a HIGH Likelihood I fail out of AP precalculus I will probably be here alot asking stupid questions this is a warning 🫡
😔
Why is the slope of the secant line necessarily equal to the average rate of change between the two points? (I know the question is trivial and the answer might be obvious to most of you but I find this kind of counterintuitive. The slope is the same as long as the two points are the same, no matter what kind of shape the function is taking between the points. This boggles my mind. An explanation that goes "By definition..." makes it even worse.)
Say you have an interval [a,b] then you would calculate the average rate with the formula (f(b)-f(a))/(b-a) right
You wanna know how much is the average rate of change
Now if you drew a line through these two points (a,f(a)) and (b,f(b)) you would get a linear function
a line
And you would notice that the slope of that line is equal to the average rate of that function if you drew a triangle
and we call that green line a secant line because it intersects at two distinct points of f
By definition, the slope of the secant line is the average rate of change between two points
jkjkjk 😂
i have created brainrot of math called mathrot let me elaborate a conversation using this mathrot "wsp dude have you been integrating and graphing to make that mtan line more proportional in a equation, yea i have been how could you tell did my omega alphnul give it away or was it limits"
magnificent speech 👏
thank you fellow summation/sigma
with?
chat i was hitting some precalc when i got a message i check and this is what my friend turned into am i cooked?
I think they're gay
wonder what makes you think that 🤨
Y'all pre calc is fun and all but this about it
what?
Pre-Calc is fun when you understand it ;-;
Hi guys I'm stuck at getting the derivative of this function, can I get an idea how to proceed?
I wouldn't use the quotient rule to be honest
expand and divide
$y = 2x^{2/3} + 2 \sqrt{2} x^{1/2 - 1/3} + x^{-1/3}$ then power rule
higher's secret twin brother
Thank you!
no problemo
Yo
Hello guys
I need references for which book I can use for Maths for class 12th boards?
can someone please explain the concept of composite functions to me?
like, for instance, how is sin(x^2) a composite function?
you have
trigfunction(something that isn't just x, )
how does it make it "composite", though?
oh so like, x^2 is a function of x?
yes
no, this is periodic cause it's a rational multiple of pi
then why is f(x)= |sin(pi x)| + cot(3x/2) not a periodic function? if its period is coming out to be 3/2pi
cause the period of |sin(pi x)| is 1
the period of cot(3x/2) is 2pi/3
the problem is that 1 is not any rational multiple of pi
or 2pi/3 is not a rational multiple of 1
for example, -2pi or 3pi/4 or 1327pi/2093 and so on
are all rational multiples of pi
so I mean $\frac{p}{q} \pi$ where $p, q \in \mathbb Z$
higher's secret twin brother
if 1 were a rational multiple of pi
then we could write $1 = \pi \frac{p}{q}$ or $\frac{q}{p} = \pi$ where $p, q \in \mathbb Z$
but pi is irrational
contradiction!
higher's secret twin brother
this is not necessarily true?
no, that's true
the periods of sin 3x and |tan(x/2)| are rational multiples of pi
in fact you can see the combined period must be 2pi
that's the least common multiple of 2pi/3 and 2pi
the least common multiple thing is not always true
makes sense, thank you
I started pre-calculus a couple of days ago and it's damn hard, and I can't understand very specific equations that I need help 😭
it's true like 90% of the time btw
!helpp
To ask for mathematics help on this server, please open your own help channel or help thread. See #❓how-to-get-help for instructions.
you can ask in a help channel
is there any other way to do this question?
not really unfortunately
you can at most eliminate options a and b, cause the answer will be positive and those options give a negative answer
and then it happens that option d is always greater than 1, use calculus or something
but 2 cos(A/2) < 2 cos(120/2) = 1
I think it's more trouble to do it this way than knowing how to simplify the given expressions
but if you are smart you can eliminate options quickly
what do i need to learn before solving such type of questions? i think it does not really fall under the "half angle formulae" category and they have started by doing the questions itself rather than providing the concept(s)
you need to learn the technique of writing 1 as sin^2 u + cos^2 u
here u = A/2 cause we use the double angle identity on sin A
and I mean why wouldn't you try u = A/2 if you want cos A/2
i mean i get you but
when i first looked at the question, my first thought was not to start with the thing written on the top right
yeah I mean when you have no idea how to get to cos A/2
it's worth simplifying one of the options since they are all so similar
these are just test-taking techniques
cause JEE and everything
not to do with actual maths in my opinion
so, hypothetically, what if we chose option d then?
like how are we supposed to know which option to start with?
well using the trick in the screenshot, you would always get $|\cos A/2 + \sin A/2|$ and $|\cos A/2 - \sin A/2|$ for all the options
higher's secret twin brother
i see
yeah but you gotta choose one option
and you do not have time to pick a wrong one in the exam
np!
valsl
expand and simplify the brackets
you'll get x^4 + something * x^2
then u can just make a new variable y, and say that y=x^2, make a new equation in terms of y and it will be in the quadratic form and u can just use the discriminant
or you could also get it into the form a(r^2 - 2)^2 + b (r^2-2)+c
then find the solutions of this quadratic
you will be left with r^2 -2 = 1st root , r^2-2 = 2nd root
not you have 2 other quadratic
solve :))
if b^2 - 4ac < 0 then the whole quadratic doesn't have any real roots and on the other case
b^2-4ac >=0 we have the roots as real
DANG!
i would have never got this idea when i was in high school
it is correct, right ?
nvm
plex idea was way simpler
t=x^2, t = 9 or t = 4, so what are the four values of x?
yea i realized
thanks
xD
i forgot t was x^2 lmfao
is there a faster way to determine only the number of roots ? cause expanding and solving for t takes time and it gives the values which i don't need
what are you trying to do?
oh
it's a question
how many roots does ... have
As many as the highest power of the polynomial
but thats the maximum amount
there could be repeated roots
or imaginary roots
if those still count as roots then i guess yeah
Uuuuuuh i mean you could kinda differentiate and set derivative = 0 at the point but youd need to know the root beforehand
Imaginary sure but repeated ones are eh
that would help you find repeated roots? how?
oh
Mmm
if it changes i guess
Not sure how itd work with triple repeated roots
So like (x-1)^3 p(x)
In an expanded form
i mean
Ah yes
it switches, andt hen it switches again
so it just keeps going
cuz the number of repeated roots is odd
Oh
Change that to (x-1)^4 then
Howll you predict that one?
then it would switch an even number of times
so it would switch
like if it was going up, now it'll go down
at x=1
How would you distinguish between 2 and 4 roots tho
It switches similarly
that is a problem
;l
,w graph (x-1)⁴
yea it switches at x=1
,w graph (1-x)^2
maybe concavity?
At this point itd be faster for them to just find all the roots lol
more concavity -> wider curve mebbe?
fr lol
I guess so
hey yeah just use curvature :D
such great idea
Lets graph the derivatives
💀
,w graph 4(x-1)^3
bro forgot the "graph" part
,w graph 2(x-1)
Argh
,w graph 6(x-1)^5
Fat better
😭 let a guy struggle
nah bro forgot the "graph" part like 4 times in a row 😭
It was just twice ayo 😭
ssuuuuuree
'
curvature of a curve $y = f(x)$ is [ \kappa = \frac{\abs{f''(x)}}{(1 + [f'(x)]^2)^{3/2}} ] the radius of the osculating circle is the inverse of curvature [ R = \frac 1\kappa = \frac{(1 + [f'(x)]^2)^{3/2}}{\abs{f''(x)}} ] which is probably what you would think of as a measure of ``fatness''
cloud
isn't concavity...sorta similar?
well concavity gives you (twice) the leading term of the 2nd order taylor polynomial (basically the "tangent parabola") whereas the osculating circle gives you the radius of the osculating circle (basically the "tangent circle"). so both of them, in some sense, are the next level up from the "slope of the tangent line"
hey can someone help me understand factoring?
i get it, but the questions they ask me on khan academy
I don't understand
x can be -1 I believe
-1-1 isnt 0, therefore it can fit in the denom
i think
right
x can be 0 tho
Can u explain?
that was wrong, basically the denominator cant equal 0 at any step in your simplification, thats where the restrictions come from
basically, x^2-1=/0 and x-1=/0
find values for x that make those equations equal 0 and those are your restrictions, aoi messed up by saying x=/0, when it can
so the answer for that problem is C i believe
X equals divided by 0?
no x cannot equal 0
Yeah
x^2-1≠0, x-1≠0
Restrictions, right?
yea
Hold on can I send another problem and maybe I can understand?
I still don’t feel like I’m getting it
yes go ahead
ok
soo like.. please break this down for me
can you explain the restrictions?
hold on sorry lemme look again
ok yeah
im pretty sure she just factored the numerator wrong
(x+2)(x-2)= x^2-4
how so?
its a difference of two squares
oh it has to be two negative two's
uhmm
wdym
nvm yeah i think it does
it should be (x-2)^2
or (x-2)(x-2)
sorry its been a minute since ive done these😭
It’s okay
I don’t understand what they mean by excluding this number, not excluding that number, etc
excluding basically means stating what x cannot equal, so when she excludes x=0, shes saying one of the values of x cannot be 0
because if you put 0 in, the denominator would equal 0 and dividing by 0 is undefined
okay, but I probably have a test coming up soon and I can't assume what values do or don't equal to x
not saying that's your problem
but it's just making things more difficult for me to understand
ok lemme write this out rq
okay
its hard to explain over discord like this
Denominator is equal to zero with x=2 not x=0
i know its just an example
when you go to multiply 4 and x, why leave 5 out?
wdym
also yeah subtracting 2 and 4 by themselves is gonna give them 0
what is that to prove?
oh sorry I was looking at the numerator and denominator at the same time
all good
so when the numerator is 0, does that mean the entire thing is just 0 at that point and the denominator doesn't matter?
basically
0/x is just 0
or 0/ any number
so undefined or still not equal to 0?
no undefined is seperate
thats why the denom cant be 0, when the numerator can
if im understanding your question right
yeah
so if it cannot equal to 0
wait okay
so if you cancel out, right?
its like canceling them out, if you were to divide them, it would be equal to 1
so is that another way of saying whatever you factored out cannot be 1 either?
hmm
idk if id put it that way
unless im misunderstanding
if the denominator is 1-x, what can x not be
ig 1?
yeah
thats how i think about restrictions
what value of x would make the denominator equal 0
😭
ok so, the restriction is the value of x that causes the fraction to become undefined, or what causes the denominator to equal 0
its an alg 2 topic as well
Does anyone know what this is? I can't find a good video to explain it
Anyone pls help T_T
sin, cos, tan in all 4 quadrants
so $\sec^2 x = \frac{1}{\cos^2 x}$ and so on
higher's secret twin brother
This trigonometry video tutorial explains how to use reference angles to evaluate trigonometric functions such as sine, cosine, tangent, secant, cosecant, and cotangent with positive and negative angles in radians and degrees.. You need to have a good understanding of right triangle trigonometry, SOHCAHTOA, 30-60-90 triangle and the 45-45-90 tr...
you just need the equation of the line passing through (-5, 1) and (-3, -2)
and the line through (1, -4) and (3, 1)
you can only split the limit like that if both limits exist
here you have a $0 \times (-\infty)$ form, so that is undefined
higher's secret twin brother
for example, take $\frac{1}{n} \cdot n$ and $\frac{1}{2n} \cdot n$ as $n \to \infty$
higher's secret twin brother
Ooh
there are multiple ways to approach the question, of course LH is possible
(infinity/infinity) works for LH too
or you could split the numerator as $\ln(e^{2n}) + \ln(1 + e^{-2n})$
and $\ln(1 + e^{-2n}) \approx e^{-2n}$ as $e^{-2n} \to 0$ by Maclaurin series
higher's secret twin brother
Brilliant! Thx
nwnw!
how to approach this question ?
in the sequence 1,4,7,10,... what's the minimum amount of elements we need to add that starts with the first element until the sum is bigger than 400 ?
so it means something like this
a1 + a1 + a2 + a1 + a2 + a3 ... > 400
which means
S1 + S2 + S3 + ... + Sn > 400
yo
what does this mean?
(n) - Number of terms
no, what's the bar over it?
Where are my bros
@ionic locust
@ionic locust
.
bump
a typo maybe
i’ve never seen something like that
maybe it’s trying to say beta / (n-1)
Bracket (n-1)
I just checked again from another website and it's simply (n-1).beta; I do not know why would they write it like that though
got it!
how did we get the second step of this?
product to sum formulae
oh wait they didn't use that they just observed that cos 60 = 1/2
i got it, thank you!
Cos 20 * cos 40 * cos 80 = sin160/ 8sin20
But sin160 = sin20
So this is just 1/8
This * cos60
Gave 1/16
Just an alternate solution
makes sense, thank you so much
what formula are we using here again?
cos(x) cos(2x).... cos((2^n)x) = $$\frac{sin(2^{n+1}x)}{(2^{n+1}sinx)}$$
Ender Doesn't Mind
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thank you!
very very handy identity
are we supposed to solve it like this or no? if yes, how do I proceed further?
why do you just take 2 tanA to the left side giving you tanA=-tanB