#geometry-and-trigonometry
1 messages · Page 279 of 1
this is not a rectangle.
uhh, how do i know that?
what do you mean
do you not know what a rectangle looks like
for one, a rectangle has four corners, while this shape has six.
oh, im thinking about overall shape, sorry.
you can view this shape as a 10 by (6+x) rectangle with a 6 by (10-x) rectangle cut out, if you want.
yep, thank you 😄
@winged pagoda
@upper karma google "lateral area of a cylinder"
the lateral area is the rectangular part
Circumference of circle
@upper karma post a picture of the problem
along with any diagram they offer
because I think you're missing something
a diameter maybe?
consider the formulae for Volume and the lateral surface area
the lateral surface area is just h*circumference (or 2 pi *r*h )
$\begin{cases}
\frac{100}{360} \cdot \pi r^2h = 20\pi cm^3 \
2\pi rh = 48 \pi cm^2
\end{cases}$
those would be the respective equations you can get from volume and lateral surface area
solving that system will get you the values of r and h
pi r^2 h = 20 pi is for the 100 degree wedge
maybe if you turn 100 degrees into radians?
ramonov:
I thought about 100/360, but wouldn't it be better if it was in radians?
you'd end up getting the same thing
@silent plank how do you make a system on LaTex?
\begin{cases}
\end{cases}
,calc 100 deg to radian
Result:
1.7453292519943 radian
additional conversions aren't really needed
consider dividing eq1 by eq2
yes
you did understand why i put that 100/360 there right?
in use
in an unused one yes.
read #❓how-to-get-help first
why have I been put on slow mode for 1 hour?
EDIT: apparently there's an AP (advanced placement) test going on in America so we all have to suffer for 1h in order to prevent widespread cheating
EDIT 2: yep
EDIT 3: also, I solved the cylinder wedge problem
ok, did you solve the cylinder wedge problem?
PS: if you can't post, close Discord and reopen
@upper karma
@silent plank
Can u help me with something quick?
it will take a few min im just confused
probably
and did you get the same result?
UPDATE: this is incorrect
@silent plank
so
whenever I do this
then I used sin=0/h
but i get different heights
oh discussions already going on in the calc channel
actually, wait
it's easy
all angles from a triangle add up to 180
20 + 18 + ? = 180
ye
142
i did it
i used sine law
but then im getting 2 different heights
i got 50.19=c
55.55=b
b and c aren't the altitudes of the triangle
,w 50.19sin(20deg)
huh
,w 55.55sin(18deg)
you didn't label the diagram properly
where
from what i can make from the blur
the work you did
yes
c is the side opposite angle C
oh right lol
i.e. AB
ohh OOPS
omg
i was more focused on the
variable
or idk what i was thinking lol
yay thanks
there might be a shortcut
$h = \frac{base \cdot tan(\alpha)tan(\beta)}{tan(\alpha)+\tan(\beta)}$
what about that
ramonov:
wow when did u learn that
i forgot, i just derived it
from tan
wow cool
it should be documented
lol
,w 100*tan(18deg)tan(20deg)/ ((tan(18deg) + (tan(20deg))
@pallid lichen
lol ye
i did it
i just mixed the
lengths up
i labelled wrong
thanks tho
🙂
sure thing
@upper karma
for this problem: https://discordapp.com/channels/268882317391429632/326138757474680852/709831134082629752
Given the cardboard inside the paper towel roll has a radius of 2cm and the distance from the center of the cardboard cylinder to the edge of the roll is 13 cm. If each paper towel had a thickness of 1 mm and the height of the paper towel roll is 19 cm, determine how long the paper towels would be when unrolled.
@upper karma
the answer is probably something at the power of 110
2 + 1.1^110 ?
no, wait...
2 pi r is the length of one ring
so it needs to be multiplied by 110, but also taken into account that the radius increases by 0.1 each time
@upper karma https://discordapp.com/channels/268882317391429632/326138757474680852/709843654109560872
I forgot to multiply the lateral area with 100/360 here
sorry
fixing it now
consider the formulae for the volume of paper when rolled and unrolled
consider the formulae for the volume of paper when rolled and unrolled
@silent plank
oh, man... that's pretty clever
why didn't I think of that?
sounds doable if you think of the unrolled paper as a giant rectangular prism with a very small height
volume 1 = volume 2
then you get the height lenght from there
the width being the radius, of course
Hello, may I have help with c? know the length is r = 41, and the center of the circle is (-1,3).
Yep
@rotund vault notice that O is the midpoint, use midpoint formula between both points
Find midpoint
Find radius
Oh you got already the midpoint
And then make it a equation of a circle
Find radius
Can somebody help😓
Using distance formula
@gilded parcel sine's law
H,k Is Center of circle
@gilded parcel understood what to do?
(X-h) + (y-k) = r^2
So just plug it in
@rotund vault
Lmk if you still need help
Thanks
Np 
Don’t even know where to start 😳
what the...
Ikr
there is nothing wrong with it
this is just proof of cosine law.
use pythagorean theorem to find b^2=DC^2+h^2
@upper karma I forgot about the surfaces on the inside 😐
marked in green
there's another one on the other side
but you have the radius, you have the height...
I'm gonna go to bed
have fun 😉
did you solve the paper towel question?
One room is 5 m long, 4 m wide, and 3 m high. Up in one corner is a spider. It sees a dead fly in the lower opposite corner. The spider heads for a walk down to the fly. How long is the shortest route the spider can take to the fly?
spindel = spider
fluga = fly
🙂
the spider got drunk along the way
Pythagoras' theorem
well apparently not
lol
does it have glider wings?
no xDDD
this way might be shorter, idk
how many metres is that?
pythagora knows
ok so
5+5 = 10
@vestal mauve as long as it's not an exam or a test, sure
the answer is not 10 sadly :/
@upper karma not shortest, not right
It like that like my@english not very good and I don’t know what it telling me
@upper karma should be sqrt 41+3
@acoustic jungle nope :/
ok if it's not sqrt(41)+3 what is it
first of all
you flatten the "room"
so it's not three dimensional
then you calculate the shortest
it was something like that, give me one check i gotta check my notes
that doesn't make sense, what is the answer?
8,6
m
so basically the spider opens a worm hole to another dimension that doesn't have a Y (up) axis?
what do you mean flatten the "room"?
so apparently you're suppose to think that the room is a box
and then you flatten it out
and from thereon you can calculate the shortest way
Think of the room as a box. Unwrap the box so you'll see all the sides. Now point out the spider's position and the position of the opposite corner.
All you'll have to use the pythagora's theorem.
,w x^2 = (3+5)^2 + 4^2
depends on which side the fly is on
the 4 meters away or 5 meters away
it might be root of 7^2+5^2
which is indeed 8.6
yeah? what if the spider falls down during the unfolding?
well this is a problem where it's legit a robot
it takes the shortest way
without fail
only success
btw the pic you made
pythagoras
unfolding doesn't mean you unfold it
64+36 = 10
it means he's traveling on an angle to the ground
then travaling on an angle to the fly
very nice.
how is it 74?
sqrt((3+4)^2+5^2)
why 3+4?
hmmm...
maybe the "room" is rotated 90 degrees?
this is a 9th grade question
lol
math checks out
wait what
where it says 4, it's suppoe to be 5
and where it says 5, it's suppose to be 4
yes, because it's rotated 90 degrees
or rather, you view it from a different angle
the spider is still "up in one corner"
doesn't specify which
kind of a weird room, tbh
if it's trig related, sure
@vestal mauve which one did you have trouble with?
I forgot about you 🙂
oof
why don't you do
use the identity
@vestal mauve
if that entire segment is 10
and GF is 1
how long do you think segment HG is?
this is just addition and subtraction
do you think it might be 10 - 1 ?
9
yes
Sorry I’m not good in math
Yes thak you
what about this?
the entire line segment is 26
and this one?
first you find the little "?"
then you can get the bigger one
@upper karma search the volume of a section of a circle
@vestal mauve did you understand these so far?
up until question 6
I just needded a like remindir
what did you get for 5) and 6)?
@vestal mauve for question 5) it's 9+11 = 20, then you subtract that from the entire thing (which is 26)
so 26 - 20 = 6
question 6) is similar. First you get segment HI and then you add that 12 to get segment HJ
@upper karma I wonder what happens to that 120 degree angle when it gets folded like this:
Hey everyone
I’m having some trouble in geometry if anyone can spare some time to help me?

Ok
don't ask, don't tell
do you know about inscribed angles?
yes
Yeah I know it
yes
But that isn’t an answer
and you want NP, which is part of that arc
Ohhhhh
got it?
Yeah thanks
sure
Just being nice
to help you understand the problem, which is what I hope I did
try posting in a questions channel?
@quartz pulsar plot it
and maybe google what an "orthocenter" is
@candid terrace search youtube for "circle theorems"
the first 2-3 videos should be enough
Ummm, I need help from someone that actually knows the material.
Ok
the people making the vids know the material
I should've been going to bed 3 hours ago
g'night
Good night😴
I was wondering how they got that answer. Can someone explain
Idk.
isnt it 1/sqrt(2) ?
I started by dividing by cos(x/3) first to get 1-tanx=0 then went from there.
But ig that's wrong.
There is nothing wrong with the answer
Yeah, ik.
they did cos(x/3)=sin(x/3) then squared both sides, converting sin^2(x/3) to 1-cos^2(x/3)
and 1/sqrt2 =sqrt2/2
thnx
I have absolutely no idea how to do this
It is what it is
You sound like my mom
I have a coodinate geometry problem. I need to find the missing coodinate (-45, unknown) this coodinate is part of a parallel line which shares the same line with another coodinate (-90, 180). The line parallel to that one has the coodinate of (0,0) and (38, -535). They both have a gradient of -0.07. I need to find the missing coodinate.
<@&286206848099549185> (Sorry for the notify)
the line connecting the points (0,0) and (38, -535) doesn't have a gradient of -0.07
@kindred girder
what have u tried?
well i found out that the cone volume is 18 pi?
and so the ice cream volume should be 9pi since its half?
what's a definition of the gradient?
and how do you find that value of m
ok
@visual mist finding the volumes isn't really needed, apply ratios of similar solids or something
how
tell me specifically how you are getting the value of -0.07
Ok
ok
(38-0/-535-0) = -0.07 aka the "m" expression
you're mixing your x and y coordinates
nah i cant explain good
ramanox u take it
ramanov
its just 1/2 cubed times the area of the cone
lol
ram is so busy XD
ik lol
How do you determine if there are one or two solutions that can be taken by a number?
if the ratio of dimenstions (of similar objects) is:
1: a
the ratio of volume is
1 : a^3
oh shit ill wait
whats depth
should've said dimensions instead of sides
anyway, you are told that for V,
the ratio is 1 : (1/2)
yes
yeh
noice
why cube root it
if the ratio of dimenstions (of similar objects) is:
1: a
the ratio of volume is
1 : a^3
..
cube root of a^3 is a
yeah
and 1: (cbrt(1/2) will be the ratio of the dimensions of the big to smaller cone
gimme video link XD
k wait
ok
lemme find one
did you understand:
if the ratio of dimenstions (of similar objects) is:
1: a
the ratio of their volume is
1 : a^3
https://youtu.be/r7m424e3Kdc idk this probably
This geometry video tutorial provides a basic introduction on similar triangles and similar figures. It explains how to find the missing side using the proportions of similar triangles and even similar trapezoids. It explains how to solve for x as it relates to missing sides...
that doesn't seem related to volume
yeah
Tutorial on Similar Polygons and Scale Factor
scale factor
same idea here
using scale factor stuff
i guess
but then the ice cream volume is half of the cone volume, why do u cube root it
https://youtu.be/03-G60uEeQs heres a good one
Learn how to use scale factors to find length, area, and volume in similar figures in this free math video tutorial by Mario's Math Tutoring. We go through some examples in this video.
0:22 How to Find the Scale Factor from A to B
1:24 Squaring the Scale Factor to Find Ratio ...
there u go
if the ratio of dimenstions (of similar objects) is:
1: a
the ratio of their volume is
1 : a^3
in your question, 1/2 would be your a^3
ok let me watch vid first
Is it my turn now?
How do you determine if there are one or two solutions that can be taken by a number?
@barren tide This
properties of sin and the unit circle
but what if its a number that isn't on the unit circle, like the example?
there are 2 solutions to:
sin(x) = c
for: (0<c<1 and 0<x<180°)
wdym by isn't on the unit circle?
(and then apply angle sum of a triangle or otherwise to determine whether the obtuse angle is a legitimate solution to the problem)
Oh so I just have to test it? fuck me
wdym by isn't on the unit circle?
they probably mean "the angle isn't an integer multiple of 30 or 45 degrees"
ya that
thnx
oh one more question
What about this? Why is it positive when it is considered in the third quadrant
It is what it is 🤷♂️
can you repost the image so i don't have to scroll
preferably one thats also clearer
like there's discord on the comp. and comps have screen cap tools
pi < 3.805 < 3pi/2
is in quadrant 3
it doesn't matter if the angle is expressed as a negative value
what matters is the position / location
here it was shifted to quadrant 3 by doing
pi - (-0.663) = pi + 0.663 ~ 3.805
Is it because it is between
pi < 3.805 < 3pi/2
is in quadrant 3
@silent plank
and negative isn't?
,w sin( -999pi - arcsin(-8/13) )
that angle is in Q3 and the sine of that will be negative
Does anyone speak german here? I'm trying to help a student and I need a better translation (than she gave me)
can anyone help with this?
@wicked raft what needs clarification?
@wicked raft A right cone has a slant height (m) twice as long as the radius of its base(r). Calculate
a) the ratio of the surface area to the base (M:A)
b) the central angle alpha of the lateral surface area
acos(dot(normalize(r), vec2(0, 1)))
Should return the angle between the two vectors in radians, right?
Yet, the angle returned seemed to neither be in degrees or in radians, I've cheched
Could anyone help me with this?
Nvm, just used wrong vectors
<@&286206848099549185>
@graceful narwhal I got it now, thanks
help i’ve been on this google form forever
Lol seems like a test @dense sky
Okok
it’s like one of are final classroom assignments and the teacher decided to put a bunch of questions
cuz.. my teacher is annoying
so instead of like a 5 question assignment
hurr durr last week so it’s a bunch of questions
State the circle's equation here on the chat.
$(x-h)² + (y-k)² = r²$
Al3dium:
@dense sky bruh you got answered already smh
what?
@vague berry just post it 
Augustus:
$cos(csc^{-1}(tan(cos^-1 1/3)))$
Augustus:
please help
its not like that
it looks like cos(csc^-1 (tan (cos^-1 (-1/3))
like arccos
arccsc
it looks like cos(csc^-1 (tan (cos^-1 (-1/3))
@vague berry so this is the question
Are calc allowed
Cos you can just plug those in
no
Calculator lol
Hm
Unit circle
umm
idk
something like that i guess
@upper karma
please dont bail on me
<@&286206848099549185>
please help
im dying out here
$tan(π+arcsin(-2/3))$
Augustus:
Test
what's troubling you?
Well like do you don't know how to start at all?
You wouldn't need to
Alright so use the fact that $\tan(a + b) = \frac{\tan(a) + \tan(b)}{1 - \tan(a)\tan(b)}$
Augustus:
Sid:
I'm a baby
I can't do that either
Wdym you can't do that, are you not allowed to?
Alright well anyways $\tan(\pi + x) = \tan(x)$
Sid:
That's because tan is pi periodic
After doing that you need to do all those triangle thingies you were talking about
To evaluate $\tan(\arcsin(-\frac23))$
Sid:
Do you know how to do that, or no?
Oh well noice
Augustus:
the -1 thing for csc and cos mean arccsc and arccos
you use cosec^{-1} or arcosec for that but yeah
Uhm well I would start by evaluating $\tan(\arccos(-\frac13))$ first using the triangle thingo
Sid:
Then again do the same triangle thing for $\cos(cosec^{-1}(\text{The thing I found}))$
Sid:
ok
ok
np
Can anyone help me with this i don't understand it Calculate the sizes of adjacent angles if one is an adjacent angle is 110 times smaller
i am unsure how to evaluate with x=1, series i still didnt do as a chapter
so i am not sure how to just plop in x and do this
Hey can someone explain the purpose of Log 10 and Natural Log?
Can anyone help me with a problem
Yes
I’m here for you
Unless it’s super hard
Send it
Ok I’ll take a picture
Yes
Cause it’s kinda big
Ok
We can handle it
It’s number 4
Ok
Just change the equation to slope intercept form
Then plug them in
Plug x intercept and see if y intercept matches
I’m sure there are other ways too
You can ask other people
But that’s my way
Probably slower than other ways
I changed it to y= 7x -8 is that the right slope intercept form
Hold on
Nah It’s y= 7/2 x -4
Try your arithmetic again
Ok
And this applies to algebra
Not geometry
I think
It’s algebra since it has to do with the slope intercept formula
I learned that when I was in algebra
Next time use #prealg-and-algebra
Ok
it comes under coordinate geo which is fine here
@silent plank Go for it
Yes
@silent plank It’s time for your lecture
You can explain it to him
If you need to
Explain in more depth
I guess
Ok I have another one it looks actually hard
Yes
Very hard
We can stand it
We are brave men
Send it!
Very brave
Can someone please help me with this I’ve tried for a while but can’t come up with the answer? 🙂
“Write a expression of the area of figure N”
It’s a pattern
I’m sorry but my English when it comes to math is not that good but i see that the increase is increasing with 2 every time
But I don’t know what to do with that info
If you know the pattern you can determine the next figure
Between figure 1 and 2 it’s increasing with 5 and between 2 and 3 it’s increasing with 7
Yes but what about if I want to figure out figure 135
Like I need an expression to explain the pattern
You said you need to find the area of figure N
Yes
Which is after figure 4?
@silent plank Help
For an example it’s usually something like “Area=2n+1” but this one is much harder
@paper oar Help
Thank you ☺️
You’re right, how did you come up with that
got a math test tmr wish me luck
Why did I get tagged
One side of the rectangle is n, the other side is n+2. I multiply them together to get n(n+2)

@paper oar
Oh
Son it’s online
Don't do it peepee.
Yes
Don’t do it
It’s not worth it
In the future you’ll have to do it by paper again
And you wouldn’t know how to do anything
Don’t cheat
Try ur best son
Thanks for the help guys!!
||how do I write 10 sentences to get 1 point across?||
Milk it
Does anyone know how to do product of slopes
I’m not sure the problem just says determine the product of the slopes of line y=10 and y=-2x-5
y=10 is equal to y=0x+10
Yessir
Find their slopes, multiply them together @upper karma
Something like this i'd assume
So the two sides of the right-angled triangle are each 10 and 14 yards long. From that you should be able to use trigonometry to find the angle the sun is coming from
English isnt the language I learn math in, so I'm not completely sure whether the answer is supposed to be the top right angle or the bottom left angle '^-^
Bottom left^
@upper karma can u help me pls
Nice.
draw a triangle
hey guys i got following problem:
Prove: If ASB is a right angle, S lies on the circle with the center M of AB as the center
and | AM | as a radius.
Anyone an idea how to start such problems?
hope this is the right channel.
mb write arctan(-2) as -arctan(2) first just to not have to deal with negative lengths
@wanton prawn this channel is occupied right now, please move
@dark sparrow What is the step after -arctan(2)?
"the" step
From the calc this comes to decimal number
no, you're kinda missing the point here, you don't need a calculator at all
anyway, you COULD simplify cos(-arctan(2)) to cos(arctan(2))
since you used the fact that arctan is odd, why not also use the fact that cos is even
and now you're dealing with positive numbers only, which is a slight step down in complexity
and it is now that you can follow ramonov's suggestion of drawing a triangle
label two of its sides 1 and 2 in a way that makes one of the angles have a tan of 2
is the answer root5/5
,w cos(arctan(-2)) = sqrt(5)/5
^
And csc x=1/sin x
And cot x=cos x / sin x
@upper karma
like that @upper karma
Would this be the final solution?
You can simplify further by doing common denominator @upper karma
Can you explain more? Would I multiply left by sinx and right by cosx, what about denominator?
By doing common deno on the upper part of the skycraper and on the bottom. You'd be doing common deno on $$\frac{1}{\cos x}+\frac{1}{\sin x}$$
And the same on the lower part
$$1+\frac{\cos x}{\sin x}$$
Al3dium:
On the first thing, multiply $\frac{1}{\cos x}$ by $\sin x$
Al3dium:
And $\frac{1}{\sin x}$ by $\cos x$
Al3dium:
While on the lower part of the skycraper, multiply $1$ times $\sin x$
Al3dium:
@upper karma
This is how common deno is done
You shouldn't have problems with this
Got it thanks
Np 
One calculator I got gives me 0.976018 for atan(1.4782) while another gives me 55.92. What am I doing wrong with the first one?
Under what situation can u get 0.976 for atan(1.4782)?
calculator settings,
radians , degrees
nope, I've tried converting 1.47 using angle to radian formula
and ive also tried converting 1.47 from radian to angle formula
why do you even need radians for tan anyways?
$\arctan(1.4782) \approx 0.976 \text{(radians)} \
\arctan(1.4782) \approx 55.92\deg$
ramonov:
uhhh
@silent plank I did that and it gives me 1.5592
I converted it using x * 180 / pi.
oh
lol turns out I converted the wrong thing
@upper karma there's a button on your calculator that makes it work in either radians, degrees, or grads
a grad is 1/400 of the circumference of a circle
on Windows 10's calc it's this button right here:

Ok thanks.
I couldn't tell because i was using a default atan() in a programming language
plot it
let me try
actually i plotted all of them
and they all look wrong
@upper karma
Just take the options one by one and calculate the radius
The one which gives equal radius in every case is correct
@pastel anchor
(particularly the "More General Case" section)
@deep trail law of cosines
i never learned that
@deep trail Finding the width of the house is the same as finding the base length of the isosceles triangle. Let's draw a height from the top of the roof to the base of the roof. How do you find the length of the side next to the base angle in the formed right triangle?
?????????????????????????????????????????????????????????????????????????????????????????????????
artist
can’t we use the law of sines 😳
.blue
How do you find B
oh
@deep trail
It's really simple at this point
my drawing was the best
i got it ty
u cant use the law of sines on that?
law of cosines makes it very easy
cosines can work aswell
Cause of the common stuff
saying we have the top angle between 2 known sides
morinkashi why would you use it
i’m used to using the law of sines and cosines
you dont have the that side so you cant do sines
Law of sines how would u find the thing for 35
I think they said they haven't learned about law of cosines/sines
Ohhh
u can use law of cosines by finding the top angle and and then you’d have an S.A.S case
(included angle thingy)
Just take the options one by one and calculate the radius
Hey why doesnt this work
cause the top angle can be found using 180 = 70 + x and solve for x
then plug in the values in the law of cosines
Why are u making it so complex
that’s easier for me 😔
law of sines easier doe
what
For this
We're supposed to find the center
I told we can go option wise and calculate by distance formula
you can use the distance formula for every pair of points ( (2,1), (x,y) -> center ; (5,2) , (x,y) ; (3,4), (x,y) ) and get a system of equations
i think it reduces to linear equations
I told we can just see from the options
And apply distance formula to every point
The option with same distance is correct
But I calculated and there's no option which satisfies this
@kind temple post your work.
what have you tried?
nope
segment is also the wrong word
set those two equal is a poor choice of words
their sum will be 360°
yeh. there is only one possible value of x
Hey can someone help me with a math question
Im trying to find the measure of the arc
BC
D;
did you learn soh cah toa yet?
yes