#geometry-and-trigonometry
1 messages · Page 75 of 1
ezpz
mhm
Anybody know the name if the geometry bc i got a test on monday and i do NOT understand this
so there are two formulas you can use
- $|u+v| = \sqrt{u^2+v^2+2uvcos(\theta)}$
Black_Gold
where $\theta$ is the angle between two vectors
Black_Gold
I’m sorry but I came from alg 1 last year 😭
Ik I probably understand it but I feel like I don’t
on the right side, every time he says u and v he means the magnitude
How did I go from special right triangle a day ago to this
This feels like a whole new class 😭
now to find the angle use --> $tan(\alpha) = \frac{usin(\theta)}{v+ucos\theta}$
where $alpha$ is angle between v and u+v
Black_Gold
these formulas are derived from that right triangle only
what does the weird 0 mean
Black_Gold
theta, it represents angle, its a greek letter
Well as it happens I have 4 angles and I don’t know which to pick
do you want the derivation?
I just started trig idk what’s derivation
do you want to know where these formulas came from??
Sure
vastly oversimplified:
imagine a right pyramid
turns out 3 of these can come together to form a rectangular prism
so the volume of a right pyramid is 1/3 of a rectangular prism
turns out this is true for any base shape though, not just squares (pyramids; rectangular prisms)
hence the volume of a cone is 1/3 of the volume of a cylinder
aight thank you
can anyone send class 11th cbse trignometic funtions questions
theta? what is the correct name T^T
ty
im year 9 but we didnt take that yet
alright.
If you are taking the side of triangle 'r'(same as cone's radius) then at that point it's no longer a triangle, it's side on circumference would be arc
This may help you guys
moew meow help with this one one
try squaring both equalities and then adding them together
thxx
Dayum, I just solved this as a subpart of physics proof i was doing
by angle chasing, triangle GEA is similar to BFC
so BF/BC = GE/GA
or that BF/1 = 1/GA, as GE = EA (isosceles) = 1
hahaa
Yup
now since GA = x, that implies BF = 1/x
npnp
Help pls
If its an isosceles then I can split it up into 2 right triangles right?
And since its congruent on all sides that must mean the angles are the same right?
But somehow my answers are wrong
can you show your work/calculations
Phone is dead so I cant at the moment
we integrate
i meant taking the area of the triangle and multiplying it by the circumference, my idea was wouldnt the area of triangle just rotate a whole circle around, thus getting us the volume? the cone is straight and not tilted
Yeah I get that
Wait let me think
Notice the equilateral triangles
And each angle of an equilateral triangle has the same angle which is?
You are right in your thought process, but if you observe carefully, you can notice that only the tip of the triangle travels through the disstance 2 pi r, while the side opposite to that vertex does not get to move at all. So it is unfair to multiply the parts of the triangle with the distance they dont cover
so you have to kind of cut the triangle into pieces that travel the same distance and multiply the area of that piece with the distance it travels... until you are done with multiplying all the pieces
the middle angle is 60 degrees. since AB is straight line, the angle to the right is 120 degrees.
since the triangle with 120 degrees is isosceles, x = 30
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
ooh i thought we were supposed to give out solution
Uhhhh one way is to apply the cosine rule in ADB and CDB and solve for CD and BD
Now you have three sides
And you can just use the herons formula
Tho i think there should be a better way
Can anyone help 😭
I’m dumb
Kay
Second….
ANSWERR PLS
😔
I will after I sleep oh yeah!
Get out
🧌
….
Is it dead
Weird cat…
Mine sleeps like a normal cat
Lalalalalalalala

I choose no thanks
Sigh fine
Buh bye..

@faint pasture I actually dont know law of cosine
Though that way is quicker
I figured it out
Uh i dont really think you can do it with just geometry as it involves angles and stuff
Ye
Yup tup
Premath uploads these type of questions
But his question solving is complex
Why is the volume of a cone half of the volume of a sphere. We are in 9th grade
it is not
1/3pi r^2 h is not the half of 4/3 pi r^3
what does this mean then:
thats what i though
they let the height = 2r
for almost no reason
and yea
its just a coincidence
if you want a proper proof of the volumes formulas thats gonna be #calculus
We get this amazing thing that the volume of a cone and sphere together make a cylinder (assuming they fit each other perfectly)
its still just a coincidence though, right?
yeah we did the integrals for proofs of the formulas
yeps (which high school is teaching integrals to 9th graders damn)
yall are lucky, i was introduced to calc for the first time in 10th grade and had to mostly self teach back then too
wait can you help me in #precalculus
ask away i can try at least
I was introduced in 12th, but i read pretty much on my own from 10th aswell
mhm, like in here it is properly taught from 11th grade cuz of physics so yea
yeah but for physics, our physics teacher gave us same basic knowledge, so that we can do the integrals in physics in 11th
💀 they were like you gonna have to learn this properly in 12th anyways, so we might as well go a little deeper
depends on what you mean by "coincidence". archimedes used this relationship between the volumes of spheres, cones, and cylinders to discover the formula for the volume of the sphere
relevant video: https://www.youtube.com/watch?v=5q_sfXY-va8
In today’s video we’ll make a little bit of mathematical history. I'll tell you about a major upgrade of one of Archimedes' greatest discoveries about the good old sphere that so far only a handful of mathematicians know about.
00:00 Intro to the baggage carousel
01:04 Archimedes baggage carousel
04:26 Inside-out animations
04:59 Inside-out di...
Useless
Do you Have the Resolution of the 1 problem?
can you translate and send again
make a straight line equation with the help of given info
like length of first and last rod, spacing b/w holes
also it would help to take the bottom of first rod as origin
Alright, I will try that now. Thanks.
This is really interesting. I would start by finding the side lengths of the triangle.
Of what triangle
I have found the rectangular
Both triangles have the area of 1 cm^2
When it comes to geometry puzzles it helps to annotate as much as possible and remember you can draw lines as you want.
I have just solved it
4 cm^2
These are all the sides i have found
Then i calculated the area of upper small triangle (1/5 cm^2), added it to the 3 cm^2 of trapezoid (given in the instructions), calculated the area of the big square and substracted the are of trapezoid + triangle from it
The sides of the small triangle i have calculated using the similarity of triangles
The answer is right, but correct me if i overcomplicated the solution or did unnecessary steps
Can you please translate?
Sorry to bother you, I wanted to ask. I have the intention of joining the Mathematics Olympiad but I'm confused about where to practice. Do you have any suggestions for websites/YouTube channels for practicing math questions, guys?
Grade ?
Website of the Olympiad? Problems from previous years
#competition-math may be more suited (see also the discord server in that channel's description)
yo how to do vector shit
im so confuse
like how to find the ratio of a point on a line doing vectors
Can someone give me a thorough explanation on how to do this please
use the pythagorean theorem
In triangle ABC, segment BD is an angle bisector of the triangle. suppose point E lies on AB. why does the reflection of E over BD have to lie on line BC?
hi
can anyone explain why if we have two triangle and all their corresponding angles are the same, then the triangles are similar and the ratio of their sides is the same? Is it because when the corresponding angles are the same, then the "shape" of triangles is the same while the size may differ
resizing a triangle doesn't affect the angles, so any two similar triangles can be thought of as the same triangle just moved around and enlarged/shrunk
and the size change affects all of the sides equally, so their ratios are preserved
okay, got it. By the way, the angles ratio doesn't equal the sides ratio?
@cunning lion
we have a theorem relating ratios of angles and sides which is the law of sines
i know it, just wanted to clarify whether it works with just angles
it does not
It doesn't?
Could you verify your question?
Actually it does
I got kind of a coordinate geometry based proof if you want it
Ok I didn't get the question then
Or nvm it isnt really coordinate
Could you explain the question?
Ah i need a diagram to explain the solution
Oh thats just like if i have a triangle ABC
Then i draw the angle bisector through A
Then the mirror image of B about the angle bisector
Will lie on AC
They just kinda changed it up a bit
Instead of B they took another point on the side
The solution doesnt change tho
Oh i get what you mean
They wanted to say BD where they said AB im kinda sure
Reflection of a point about a line passing through it doesnt make sense and they defined BD
So ig yea they meant BD
I know the proof but i need a diagram to explain it properly and i dont have anything to draw it on
But basically let the side AB and angle ABC be fixed, ie all we can do to the triangle is adjust AC
So if we choose AC such that ABC is isoceless the mirror image of B will lie at C
However you can extend the side AC much as you want the mirror image wont change up
So we again fix up AC to be the original length
And the mirror image still lies on there
Yea in short that
Oh hell naw
Oh..
I just had to do this proof for coordinate geometry
Oh
Mmmm
If you get any good questions , ping me please I would like to try
Because im preparing for the 2nd stage for representing my country in IMO , I just cleared the first stage
ABC isosceles triangle with angle A = 80°, base BC.
Inside of the triangle is point M such that CBM = 30°, BCM = 10°.
Find angle AMC
😊😊
Hi, how do i solve this one
I have already calculated the area of the left right triangle
But what about something that is similar to a circle's sector, but is not
I mean, the sector where "Blue Area" is written
I know it is not a part of a small circle, so i dont know how to calculate its area
Thanks
Okay, so it has 4 cm side and arctan(3) + 60° angle
Uhmm one of its angles is 30° actualy
How did you figure it out?
Got a study question. I'm taking this trig course that doesn't have any lectures. It's basically read the chapter, then do homework problems. Then there's a huge playlist of trig videos. I don't know if this is normal for online school.
Anyways. Would it be more efficient to work on the problems as I'm reading? How do other folks study?
Everyone studies differently
But my personal approach is... go straight to the problems. and when you encounter some term your don't understand, find it in the lectures 🤣
Lol. Thank you! I think I'm going to take this approach to the next section.
does anyone know how to explain geometry proofs to me😔
show me notes and i probably can
if you are allowed a calculator you could try an exponential regression
doubt it would work with only 2 points
yea idk then
chat gpt it
Do you know the exponential model general function?
mb gng i turned ts in idgaf anymore😭😭😭
☠️
yeah like i got notes from class but like i would keep applying it and it would say its wrong😭
br
yes but i redrew it cuz she put the wrong degrees in hers
how do you know she put the degrees wrong?
she told us and i didnt wanna have to explain it so i just redid it
she put 60 instead of 45
oh
do yk how to do it
i mean you know how a 45 45 90 triangle has side lengths 1:1:sqrt(2) where the hypotenuse is the sqrt(2)?
yes
can you see that your diagram is a 45-45-90 triangle?
i mean the triangle created between the person on the boat and the tower
oh so would i be like tan45=5280+x/1454
because the angle of elevation is 45 degrees, and the tower goes straight up
nah that was fast 😂
i just didnt even consider that until you reminded me 45-45-90s exist
😂
what is it?
yeah
which if i used the 60 instead of 45 id have 1454 sqrt3
that is actually very weird
she made it
💀
but shes like hella smart so im lost
i think the answer is fine to be negative
logically it doesnt make sense but im not sure if she thought that through
like her answer is negative as well
if she wouldve said 30 degrees it would make sense
i guess the boat is just on the shore 😂
here lemme show u what she drew
ok
XD
im soooooooooooooooo lost lol
like that makes sense right??
where does she get the denominator 3
yeah, that makes sense, except in the sense that the distance is still negative
you mean the square root 3?
oh
she used 30 degree elevation that time ☠️
🤣
tan(30 deg) = sqrt(3)/3
tan(60 deg) = sqrt(3)
tan(45 deg) = 1
💀
right thats exactly what im thinking
bro whatever hopefully i get partial credit for setting it up right
i bet you'd get full credit if the problem is screwed up 💀
if you answer the question as is
i mean if theres one similar on the test
correctly
here this was the other one
thats the answer but coukd u explain why i use tan -1 cuz she never even showed us that
ok so tan(x) = 9.3/7.4, that makes sense right?
YES
thats the inverse tangent function
sry caps
i mean isnt it cotangent
no, thats the reciprocal
oh
of tangent
i thought tan-1 was cot
okay so how do i know to use that?
or inverse tangent
basically, if you apply an inverse function to a function of x, you get x back
so arctan(tan(x)) = x
so, if tan(x) = 9.3/7.4, you can take the arctan of both sides
arctan(tan(x)) = arctan(9.3/7.4)
x = arctan(9.3/7.4)
does that make sense or 💀
like tan(45 degrees) = 1, so arctan(1) = 45 degrees
because arctan(tan(45 degrees)) = arctan(1)
45 degrees = arctan(1)
arctan is the inverse of tan
arctan(x) = tan^(-1)(x)
so if y = tan(x), x = arctan(y)
(theres domain restrictions but that doesnt matter for triangles here)
it just does the opposite of what tangent does
okay so how do i know like when to use that? like when i am trying to find the angle of depression?
yeah, when you know tan(x) = something and you need to find x
you want to know the angle
then you can use arctangent
x = arctan(something)
and then you can probably just plug into a calculator lol
omg ur lying so tanX is tan^-1??
times whatever
so like tanX=(7.4/9.3) so i can do tan-1(7.4/9.3)
no what?
yes
x = tan^(-1) (7.4/9.3)
and then you plug that into a calculator because no one in their sane mind would manually estimate that
ohhhhhh i see omg okay i get it
this is a joke btw
oh cool
dumb mistakes will be the death of me
nah i fell for it too
😭
just blame the brain not functioning correctly at that moment 100%
ive been mixing up cos and tan for like the past 2 days and its actually driving me insane
true not my fault
get sleep, drink water, practice 😔
try to use brain more ✅
this is actually top tier tip for not making mistake
use brain more
the practice makes me wanna die cuz i panic so much abt this stupid class
😂
funny i feel like practicing would make you panic less...
idk i like over practice and then blank out when its infront of me
yea honestly thats relatable XD
whatever hopefully that doesnt happen tmrw cuz it caused me to fail my first one
just think through everything if you can
@trail tendon , Bro how did you get the "very active tag"?like i live in India so i can't help when its night here and thats when most of the convo happen because of people living in USA, also where are you from
i dont know how i got it, it just appeared one day probably cuz i talk a lot 💀
im from USA yea
well, you can see that MNL is 90 degrees, and NPL is 90 degrees, right?
i do see that yes
so MNL means if you start at M, then go to N, then go to L
Does anyone have any trigonometry tips and tricks to help with memorizing values on the unit circle
right bro i need that
oh i know how to get to MNL just NPL and MPN
no
becausae if i find NPL and MPN i could find MNL
I have some holes in my understanding I feel like im so close 😭
i dont understand lowkey dont see the vision
if you have triangles LPN and NPM, the corresponding sides have to match up. so LN is the hypotenuse, just as NM is the hypotenuse. LP is the long side, just as NP is the long side. PN is the short side (of triangle LPN), just as PM is the short side (of triangle NPM)
wait i read what you said wrong
ok that i see the vision
LN is hupotenuse and MN is hypotenuyse
yeah
mhm
so if i start at the right angle
for example i said
triangle pln
it would be
npm?
PLN goes along the long side and then it goes along the hypotenuse
NPM goes along the long side and then it goes along the short side.
so those wouldn't correspond, right?
but if you went like PNM
then you go along the long side and then along the hypotenuse
so that would correspond to PLN
UHH
XD
NMP goes along the hypotenuse and then the short side, right?
(i'm leaving out the last but technically then it goes along the long side because its a triangle)
it does the hypotenuse
NM is the hypotenuse
HOLD ON
TRIANGLE PLN
WOUD BE SIMILAR TO
NPM
DID I GET I
PLN would be congruent to PNM
they both go through the long side, then the hypotenuse, then the short side
NO 3HQW6
mhm
where?
im talking about the example i sent earlier
because based on this example i js send triangle KPM is similar to MPL
and it starts with M
PLN -> goes from P to L, then L to N
since its the last letter of the first triangle
then N to P but just considering the first two constructions is enough to identify it
lets say i do triangle NLP
dont my similarity triangle has to start with P
it would be triangle PNM would it
then you go from N to L, and then L to P
hypotenuse to the right angle
so NLP would be going along the hypotenuse, and then going along the long side
first NL goes along the hypotenuse
first PN goes along the long side
so those wouldn't be the same
however, if you did like MNP
it goes from M to N , and then N to P
first it goes through the hypotenuse MN, then it goes through the long side NP
this is confusing
similar to how NLP goes through the hypotenuse NL, and then through the long side LP
😔
i dont know the greatest technical terminology for it lol
im saying "goes through" i don't really know how ur supposed to say it
but like thats the order
so does NPL similiar to MNP
if you walked from N to L to P, you went along NLP
first you went along NL (the hypotenuse route) , then you went along LP (the long side route)
no, but NLP is similar to MNP
but its not similar to LMN XD
because angle LPN is a right angle
the long side is LN yeah...
sorry uh
the hypotenuse is LN
the "long side" i was using was the longest side that wasnt the hypotenuse lol
oh
i thought hypotenuse are the longest side
i was just calling it long side because it was longer than the short side and the hypotenuse was diffferent
my bad i shoulda clarified 😭
yup
NO
what
i was taught that the middle letter of a triangle is always a right angle
if you start at P, go to N, then go to L, you traverse the short leg and then you traverse the hypotenuse
if you start at P, go to M, then go to N, you traverse the short leg and then the hypotenuse
you should probably add arrows i dont know which one was first 💀
no...
if you're considering an angle, <PLM, then you are talking about <L
but theres no guarentee of a right angle and we're talking about triangle orientation and not the angles
uh oh
what 💀
yea
why are they flipped
wdym?
back to this problem
my teacher took the first letter of the first triangle
and the last letter of the second triangle
then filled in the middle letter
i dont se that pattern for the answert i put
what does "the first letter of the first triangle" mean
you see triangle KPM
the first letter is K
and the last letter of triangle KML is L
and for the middle letter you just fil in whats missing
oh i see
im pretty sure that only worked here because you happened to pass through your last destination 💀
bruht
she literallyt said that
why is she giving me problem that ion know how to do
did she say that for in general, or for that problem
in general
💀
did you go through these and you think the answer is D or you're not sure?
ok
for LMN, first you go along LM, and then you go MN, does that make sense or nah?
like you go from L to M to N
if you start at L, then go to M, then go to N
its the same as starting at L, walking the distance of LM, then walking the distance of MN
i mean i get what you['re saying
so for LMN, first you walk the hypotenuse, then you walk the shortest leg, right?
it makes sense so far yes?
did you get the last one?
i dont wanna spend too much time on one, i partially understood it but i need to move on
i still got a lot
well the answer you selected was correct so 😂
can you create ratios for this one? (based on similar triangles)
:<
do you know that the ratio sides of similar triangles are the same?
like this?
i just drew each triangle i saw within this triangle, and you can tell they are similar because of the angles
Can anyone figure out the longest pole that can fit through this corridor without using a calculator
r u asking for help or r u just.. asking
Helpp btw
do u know how to find a?
good
so now look at this triangle
u know the angle and the opposite side
do u know any relation that can give you the length of the hypotenuse y?
oh ur wondering how to find the sine value without a calculator
yeaahh
generally this is impossible
unless u have a table of sines
which im guessing u dont
so if u dont have a calculator u can leave it as sin(37.5)
well sin(37 degree) is approximately equal to 3/5 or 0.6
you got the answer right? i just got here
,,\sin^{-1}\theta+\cos^{-1}\theta=\frac{\pi}{2}
0_א
I'm not sure, and I think the maximum value I got might be wrong
all the info shown is given right??
yeahh
yeah the answer seems to be correct, but i might have a way to prove it
i'll need some time to write it down
is this a software you can type in??
I can prove it with a trig identity, but it's so complex
Goodnotess btw
Thanksssss
what was your idea regarding the proof??
I just manually proved sin 37.5 using double-angle and half angle trigon identities
3:4:5 triangle
Yeah exactly
Express an angle of 1.26c/rad in degrees & minutes.
Before converting the answer to degrees and minutes, is it 72.18 Degrees or 72.19?
hello
ridiculous
,w 1.26 gradians / radians
do you have more digits of what you got?
if the digit after the 8 is 5 or higher, round up, so 72.19
if it's 4 or below, round down, so 72.18
go and check the info first instead of just rounding it off. Are you so high up that you cannot bend your knees...
I don't even know what c is
why the heck are you so rude
rad
so 1.26 radians right
do not mistake the truth for rudeness
,w 1.26 * 180/pi
well I should ask you why you are rounding early then
it's not equal to 72.18 degrees or 72.19 degrees exactly
ok u r dumb and will cease all communication w/ u)
just wanted to confirm, tnkz
"ok u are dumb, thanks"
How are they not banned yet
<@&268886789983436800>
gotta ping mods sooner
please don't be rude to others.
the discussion here tends to prioritize superficial intelligence focusing on surfacelevel interactions rather than engaging with the profound themes and complexities that this channel aims to explore
homie if you cant understand the surface, good luck with the profound stuff
i got sniped
maybe I should come back in 5000yrs when intelligence has increased
ciao ciao ^^
I can see your point, but the emphasis on surface interactions is merely a byproduct of recursive semiotic structures, where profundity dissolves into performative cognitive oscillations, rendering thematic depth an illusory construct within post-structural discourse.
?
let the height of both triangles be h
then you can set up simultaneous equations for both the big and the small triangles, in terms of both x and h
using tangent
how do i set up the simultaneous equations with tan?
well tan(angle) = opp/adj right
so can you set up an equation like this for the triangle with 43 deg?
tan(43) = 2?
h
yep!
okay what's the side adjacent to 43 degrees?
so the adjacent side is not the opposite side, and it's also not the hypotenuse
2
for the other triangle would it be tan(31) = h/x
nearly......
draw the big triangle out
the adjacent side is not x
is it not? it can't be O, would it be H?
no, the adjacent side is x + something
x + 2?
yep
so tan(31) = h/x+2
yep!
now from tan(43) = h/2
you get 2 tan(43) = h
can you do something similar to tan(31) = h/(x + 2)? so that you get rid of the fraction?
2x tan(31) = h ?
oh ok
and then you can combine 2 tan(43) = h and (x + 2) tan(31) = h !
||2 tan(43) = (x + 2) tan(31)
2 tan(43) = x tan(31) + 2 tan(31)
2 tan(43) - 2 tan(31) = x tan(31)
(2 tan(43) - 2 tan(31))/(tan(31)) = x||
quick
need help
i got 239.1 cuz the teacher taught us to subtract the quadrant degree with the one you get from doing tan^-1 (y/x)
if the x component is negative then you should add 180° to the angle
oh
💀
i thought you always subtracted
god this delta math took me a hour 30 to do prob
and i got a test on this in 2 days
Cool
Send here
.
It is an exercise that got in my mind. Given the right triangle ABC, two triangles can be formed by drawing a line that bisects the right angle and intersects the point N, a line perpendicular to AB that intersects point N and a line perpendicular to AC that intersects point N. Show that the figure formed by the points AMNO is either a square or a rectangle.
Given that AMN is a triangle and that line AN bisects the angle BAC, the angles of the triangle AMN are 90, 45 and 45, because 180 = 90 + 45 + x.
That being the case, side AM is equal to side MN.
Angle NAO is equal to the angle MAN, AN is equal to AN, angle ANO is equal to angle ANM, therefore the triangle AMN is congruent to the trianglr ANO by ASA, hence, figure AMNO is a square
Is this right?
Hii I have a question abt trig:
if sin^-1 x = arcsin x rather than csc x, is sin^-2 = arcsin^2 or csc^2 x?
I know that trig function to the -1 makes it an inverse, but I was just wondering abt all other negative numbers
$\sin^{-2} (x)$ is bad notation and should be avoided
south
but it would be csc^2 x
I need help finding h.
let the distance of B from the base of the height be x
so you have h/x = tan 60
can you set up a similar equation for the 45 degree angle?
(in fact the 45 makes x really easy to figure out, since you have a right triangle haha)
$\sin^{-1}(x)$ is for inverse function only. You can write $(\sin(x))^{-2}$ to mean $\csc^2(x)$ or write $(\sin^{-1}(x))^2$ to mean $\arcsin^2(x)$
҉C ҉l ҉ø ҉s ҉e ҉r
I already did that but I don’t know what you mean by setting up a similar equation for the other angle
h/(x + 10) = tan(45)
np
I got h = √3 * (x + 10) but I forgot to mention that the result needs to be a rounded off number in meters. How do I get that from this result?
tan(45) = 1
that's weird cause h = x + 10 so you went wrong somewhere
so (x + 10)/x = sqrt(3)
x + 10 = sqrt(3) x
x - sqrt(3) x = -10
x = -10/(1 - sqrt(3))
and h = -10/(1 - sqrt(3)) + 10 so round that to the nearest m
You’re right. I messed up the value of tan(45)
Okay, thank you! So should I only use the notation sin^n (x) when n>0 and use (sin x)^n instead when n<0?
yep
I mean $\sin^1 (x)$ looks weird
south
but yeah apart from that, yes
Does anyone know how to solve this problem?
The first one:
Minute hand rotates with 6° per minute (360°/60 minutes), hour hand rotates with 360/ degrees per second (24 hour is 1440 minutes). So we need to determine the time when two hands meet each other, so the angle between 12:00 and the minute hand equals the angle between 12:00 and the hour hand. X is this time.
x * 6 = 150 + x*360/1440. The answer is x equals 26 minutes and around 5 seconds
05:26:05
I was following along until it says divide the interval between the two vertical asymptotes. Where on earth are they getting those numbers from?
the length of the interval is (pi/2 - 0) = pi/2
each subinterval should have 1/4 of that length
therefore each subinterval should have length (1/4)*(pi/2)
I'm not sure I understand can you show me how you would setup an equation for a couple of them and mark where you're getting the numbers from?
if you want to divide something into 4 equal parts, mathematically that corresponds to dividing by 4
I understand now and I feel a bit stupid but why on earth would they draw the number line so inaccurately?
Do you have to know Half/Double angle formulas
Or do you not have to and do something else
They do feel stupid to me
the double angle identities are special case of the angle addition identities
and the half angle identities are a rearrangement of the double angle identity for cosine
you don't have to but they're good to know, makes sum stuff easier/accessible later. Depends what u mean by have to.
I dont know exactly what youre given, but I would guess that you just find the midpoint between two points that are opposite of the line
@wheat granite
Its this
I understand that the line of symmetry has y
But Im not sure if its y=0 or y=-r
Okay thank you so much
Where would y=-r be placed
?
It was y=-r
I got it wrong
THanks anyway
oh wait sorry I missed your message and didnt realize you were looking for a 2nd line of symmetry, I thought you mean the x one
If I somehow end up with a situation like this in a two-collumn proof, what reason can I give for angles a and 1 being congruent? (the white lines are the same)
Do you have an example
sin(2a) = sin(a+a)
Thank you
idk if this is the right place to ask about 3d transformations, but heres my question:
assume you have a point P at (1 ,3, 1)
you want to scale it by 2, rotate about the y axis by 45 deg and the x axis by 30 deg, then you to want to transalte it by (2, 0, -1)
that's not a question
forget to mention "where will that point be?"
By the way, which grade are you in?
You say rotate by 45 degrees, but you don't say in which direction.
(x, y, z) --scale--> (2x, 2y, 2z) --rotate y--> (2x cos(p45°) - 2z sin(p45°), 2y, 2x sin(p45°) + 2z cos(p45°)) := (x', 2y, z') --rotate x--> (x' 2y, z')
(x', 2y cos(q30°) - z' sin(q30°), 2y sin(q30°) + z' cos(q30°)) --translate--> (x' + 2, 2y cos(q30°) - z' sin(q30°), 2y sin(q30°) + z' cos(q30°) - 1)
p and q are +1 or -1 depending on the direction of each rotation
oh mb, i apologise 😅 but how have u done this? i was looking at one of the given slides and they have done this
oh with homogeneous coords you just google what the correct matrix for each transformation is and then let computer do its thing
whhatt, how? i have a online (open book) test on this soon
which part do you not understand?
you form your vector with your x, y, z and w = 1 (pretty sure, double check with the book)
then you figure out what the matrix for each transformation is
again double check with book or online resources
then you apply them in order
reading from right to left
S - scaling
R_2 - rotate
R_1 - rotate
T - translate
um so i understand that the order of caluations go this way but what i dont understand is why the second rotation is calcauted before the first and both the rotaton stuff is inverted
i think that's just a naming thing
hm?
R_2 applies before R_1
it seems to say something about inverses
which you left out
but if you wanna do like f(g(x))
and then you want to get back to x you do g^-1(f^-1(f(g(x))))
so that you cancel them out
so if you are undoing transformations then the naming makes sense
otherwise it's weird
How is this a parallelogram in the first place?
If I got the props of parallelogram right, then it doesn’t make sense bc equilateral triangle but 8 , 6?
how am I supposed to figure this out? I don't have a cot function on my ti84 and even if I did it would give it to me as a decimal
Remember the definition of cot
Aider moi s'il vous plaît
Je vais essayer
Merci infiniment
Je suis vraiment confus sur cette question ? Je ne l'ai tout simplement pas fait depuis un moment. Je ne sais pas ce que je suis censé faire
Reflect one of the points over the line. Shortest path is a straight line.
So angles should be equal
.
Consider an n-sided polygon.
What is to be found is the number of in it.
Let the first point be A.
We move Anti-clockwise.
From point A, the number of diagonals (on observation) = n-3 (in which we excluded from A to U - the last point and B - the adjacent point).
For this (from point B) there are n-3 diagonals again (without any re-ocurrence of any diagonal).
Things become a little sus for point C.
I never learned this yet 😭
This is not a subject to be learnt; it's logic.
I don’t use logic that much
No problem.
Oh it actually makes sense
I never thought of reflecting the point
I thought it was already equal by four parts
We can see that the diagonal AC has been considered again (it was previously considered for the first case).
So we subtract 1 from (n-3). We get (n-3) - 1 diagonals for this.
Now for point D there are two re-occurrences.
AD and AB.
So we subtract two.
We get (n-3) - 2 diagonals.
😼👍
Let the last two points be P_(n-1) and P_(n-2).
We can find the number of diagonals (without coincidence) for S (because for T and U all diagonals will be repeated).
For C which was the P_3 point, there were (n-3) - (3-2) diagonals.
On observing we can generalize this for a give point P_k (considering first point as A).
Number of non-repeated diagonals from P_k in this polygon of n sides = (n-3) - (k-2) = n - 3 - k + 2 = n-k-1
Tada!
S is the P_(n-2) point.
Observing the pattern we get it has (n-3) - (n-2-2) diagonals which equals n-3 - n + 2 + 2 = 1 diagonal.
The number of points (including S and C) between S and C = n-4.
In conclusion the total number of diagonals can be given as follows:
(n-3)(n-2) - (n-4)(n-3)/2 = n(n-3)/2
Here's the breakdown of each part:
For the 'without subtraction' part for the diagonals for a given point we have n-3.
Now it continues till S [which is (n-2)].
So we multiply (n-3) and n-2 to get (n-3)(n-2).
The subtraction part continues till S (from C).
So we subtract the summation of the natural numbers from k = 1 to k = n-4 (since the number of diagonals to be subtracted for the n-2 point = n-(n-2) - 1 = n + 2 - 1 = 1.
And the difference between the location, aka the number (for example, 1, 2, 3...., etc.) and the second part of the term (n-k) where n-k = the subtraction to be made for the point n-k+2.
_So that thing for S is (n-4).
_So finally the thing that we have to subtract = the summation of natural numbers from 1 to n-4 = (n-4)(n-3)/2.
The final formula for this calculation becomes:
(n-3)(n-2) - (n-4)(n-3)/2
= (n-3)[(n-2) - (n-4)/2]
= (n-3)[{2(n-2) - (n-4)}/2]
= (n-3)(n)/2
Which is the required formula.
So the question I am asking is:
Are all the steps of my monumental proof correct?
I know that all of it is correct but I would like to hear praise from others.
Can someone help me please

Well
It is a question that came from my mind
Given a conic section of height h and radios r, what function describes the change of r as h grows or decreases?
Damn good
But I would prefer combinatorics here
Hmm.. there are n points and each point can be connected to n-3 other points by a diagonal.
n(n-3) will be each diagonal counted twice, so to get the answer just divide by 2
n(n-3)/2
how
Yeah i learned it like this too
in this figure where all the diagonals are joined of a 21-sided regular polygon, how many triangles have been formed in total (every triangle)
inside the polygon, as small as a bacteria and also including triangle formed by the vertices of the polygon
Found a pdf about this https://cs.uwaterloo.ca/journals/JIS/sommars/triangle.pdf
i am just one ahead of them
can anyone calculate this for me
for number of sides = 21
i am invisible
why would you specifically want to do it using Heron's
just note that the perpendicular height of W above XY and YZ is the same
yep i have 3 solutions without heron's
if you insist
but i want to do it with heron's because i'm learning what's going wrong
😭
can u help me
is this where heron's fails or something because not sufficient information?
use the fact that cos(x) = -cos(180 deg - x) and then cosine rule, that might work
i thought of it but like
wouldn't that give negative measure lol
$\frac{XY^2 + YW^2 - XW^2}{2 \cdot XY \cdot YW} = -\frac{YZ^2 + YW^2 - WZ^2}{2 \cdot YZ \cdot YW}$
south
nice thing is using that argument you can have sin(x) = sin(180 - x) and yet another proof to show that the area is equal
oh wait
yeah I was thinking along similar lines
i think u got it 😭
basically if we have a way to relate XW and WZ somehow
$XY^2 + YW^2 - XW^2 + YZ^2 + YW^2 - WZ^2 = 0$
$2 XY^2 + 2 YW^2 - (XW^2 + WZ^2) = 0$
south
it's going to be hell algebraically
I think it will work somehow but don't ask me
u mean it's possible?
ye
wow
then I think this form would be the most useful
so if we let a = XY and b = YW
and a' = YZ and b' = YW for the other triangle
we just need to consider a^2 + b^2 - c^2
ah so $XY^2 + YW^2 - XW^2 = WZ^2 - XY^2 - YW^2$
south
so $(XY^2 + YW^2 - XW)^2 = (XY^2 + YW^2 - ZW^2)^2 = (YZ^2 + YW^2 - ZW)^2$ hence proven
south
thankss
@nocturne remnant (sorry for ping) helped me solve it
😭
nw
Is it possible to use the similarity of triangles to find the height of the smaller conic section?
I thought about something like this
The height of the small conic section is 12
guys what do i need to know to learn trigonometry
Everything that is in your geometry textbook before trigonometry 🤔
Isn't just angles and triangles and circles enough
Anyway
If I multiply the area of the triangle by the conic base's circumference, what figure will I have
geometric trig is 🤮
Hello I have this in my home work which is just really practice questions. And I can not seem to figure out exactly how to solve this using sine
I've been trying but nothing seems to add up
i cant try it rn but maybe law of sine and law of cosine
How can I find the answer of tan(135) ?
let's say I don't know how to find the answer of trigonometry functions when the theta value is over 90 degrees.
@maiden brook yes I believe it is law of sines
why?
i mean it's 135 degrees
but how can we find the answer with 45 degrees for that?
nonsense to me
do you know about the unit circle?
why are u pinging me
because theyre equal
i mean not fully equal since one of them is negative
thanks for your image
but what's that tangent line
tan axis
i am not finding any relationship between Tan func and that line
ok so in the unit circle, the y axis represents the sine and the x axis the cossine, right?
all the other trigonometric functions like tan, csc and cot also do have lines that represent them
that one is for tan
really?
this is the first time i hear
now i think i need to understand why they have those lines.
I will show u what i am thinking of trigonometry funcs
ok
yeah because usually you don't need it, but that doesn't mean it's not there
wait let me try to find an image of the full unit circle
thanks