#geometry-and-trigonometry
1 messages · Page 196 of 1
can you explain what you mean by flipping both sides
yeah
what do you think the solution for x should be?
2
yeah
yeah?
One way to achieve this is to take the reciprocal of both sides
Which is also the same as taking both sides to the -1 power
you mean ^-1
Yeah
i dont understand what you mean by flipping both sides tho
ohhhhh
wait so your saying
1/x=1/2
and the flipping being
x/1=2/1
and then solving it
so its on the bottom
bc when something is on the bottom you can times it with whats on the other side to solve it
if that makes sense?
cross multiplying??
yeah
could someone please explain to me how they're solving this
i can't understand this no matter how hard i tried
i know the formula for incenter and shoelace but I can't visualize this image nor establish proper coordinates for everything
Autistic Hoodie:
What is the vector of the normal?
n(A,B,C)?
Doesn't seem to be right... :/
Found the solution
Apparently I am supposed to use the algebric form of the plane formula
Which is
$A(x-x_0)+B(y-y_0)+C(z-z_0) = 0$
Autistic Hoodie:
And n(A,B,C) is the normal of that plane
Actually I only need to know sin2 - cos2 = tan2 - 1
$\sin +\frac \cos \sin - \frac \cos \sin + \cos $
Tuong:
?
$\sin^2-\cos^2=\tan^2-1$
Tuong:
doesn't look true

damn my text book prints wrong stuff
@gritty siren that is only the denominator part
let me write whole stuff
sin+cos/sin-cos+sin-cos÷sin+cos=2sec^2÷tan^2-1
$\sin+\frac\cos\sin-\cos+\sin-\frac\cos\sin+\cos$
Tuong:
no no wrong
1=cos²/cos²
yes
use that

i love math a lot but i acc cannot stand trigo
i need help
for question vi, we are meant to use the R formula
so we are allowed to pick between sin and cos, as long as we put it correctly
but this bitchass question
1 is wrong and 2 is correct. why is 1 wrong. what mistake did i do
Test
I'm trying to solve this problem
There are two lines, find the parameter lambda so that the two lines intersect
$a... \frac{x-2}{\lambda} = \frac{y-1}{1} = \frac{z-2}{0} \ b... \frac{x-5}{2} = \frac{y-2}{3} = \frac{z-3}{1}$
Autistic Hoodie:
Right so the first part is to convert the two lines in parametric form
dividing by 0
No
It doesn't mean that
Apparently dividing by zero in that is not really dividing by zero, it's just a way of writing it. it does not have the same meaning
Anyways
$a... \ x = 2 + \lambda t \ y = 1+t \ z = 2$
Autistic Hoodie:
$b... \ x = 5+2t \ y = 2 + 3t \ z = 3 + t$
Autistic Hoodie:
Alright, that's correct
Now, I am supposed to find lambda
$2+ \lambda t = 5 + 2t \ 1 + t = 2 + 3t \ 2 = 3 + t$
Autistic Hoodie:
From this
Okay I found the problem
I chose the last one because it's the simplest to answer but apparently I need to choose one that has t on both sides
From the last one I get that t = -1
And from the middle one I get that t = -1/2
t = -1/2 is the correct answer
Or now...
hmm
Or not...
Okay, I found out the problem
I have to use different variables for the perametric form of the lines
Which means that the line b is actually
$b... \ x = 5+2u \ y = 2 + 3u \ z = 3 + u$
Autistic Hoodie:
Than I put the equal one to another
$2+ \lambda t = 5 + 2u \ 1 + t = 2 + 3u \ 2 = 3 + u$
Autistic Hoodie:

Anyways, say we have a paralellogram ABCD
AB = 8m
AD = 2m
And we know the paralellograms area
Can we find angle DAB?
umm
Anyone?
I formed an equation:
2 * (1/2) * 8m * 2m * sin (DAB) = area
But
That doesn't give a correct answer
Even though it should
No?
uhh
the A B C D go clockwise and the A is at the top left corner of the paralellogram
and the parallelograms top slants towards the right
we have the area
oh whats the area, sorry??
11.05m^2
,w 11.05/16
,w arcsin(0.690625)
,w 0.762353 convert to degrees
that's what I got
so that's apparently wrong ?
however the correct answer is 136.4
this gave me a headache
,w 180 - 43.68
yea
why'd we subtract from 180 now?
arcsin(x) cant spit out a value that's not in between [-90 , 90]
in this case DAB is greater than 90
so we need to subtract the ans from 180
are we talking in radians rn?
oh sorry
it's 180/pi right?
what's 180/pi ?
like it's the ratio used to convert from radians to degrees and vice versa
soap:
c?
c for radian
ah
like that circle thing used to show that it's in degrees
yeah no i realized
but how does arcsin's range being from -90 to 90 mean subtracting the answer from 180?

this gotta do wiht unit circle
from the parallelogram itself, you can tell that the angle is more than 180
isn't that like the easier explanation
i mean more than 90
sorry
more than 180?
90
okay
and the value you got is an acute value
because when u do trigo and that formula, it gives u in a triangle form, hence always acute
do u follow??
yeah but the question didnt require the value to be obtuse
u can seen that sin of theta and 180 - theta is the same
it didn't but the fact that it's a parallelogram tells u that it should not be an acute angle
because logically, DAB is more than 90
hmm, yeah youre right spider
a lot of the times, you'll get an acute angle but the question requires obtuse due to the question giving diagrams etc
i hope it helped?? idk hahah sorry



Taha:
Compile Error! Click the
reaction for details. (You may edit your message)
uhh
Guys whats the difference between a infinite series and an infinite sequence
,tex sin^{-1} (sin (a)) = a
Taha:
Compile Error! Click the
reaction for details. (You may edit your message)
Not always, for example a = 100
You're working in degrees!
!
Notice however that sin(100) = sin(80)
Degree users rise up!
So sin¯¹(sin(x)) will be a value within -90 ≤ x ≤ 90 that has the same sin of x
Cool cool. Feel free to ask if you have anything else!
What is the correct way of doing dot products of two vectors?
$\vec{p} = \lambda a + 17b \ \vec{q} = 3a - b \ |a| = 2 \ |b| = 5 \ \angle (a,b) = \frac{2\pi}{3}$
Autistic Hoodie:
$\vec{p} \cdot\vec{q} = (\lambda a + 17b)(3a-b)$
Autistic Hoodie:
The 80's:
How do you test if points are coplanar?
For example I have three points
$A(0,0,2)\B(0,1,6)\C(-2-1,4)$
Autistic Hoodie:
Alright, my question doesn't make sense
3 points are always coplanar, lol.
But I learned how to test if 4 points are coplanar
From those 4 points you make 3 vectors and calculate their mixed product and if it is 0, they are coplanar
hello
I was completely lost on this
what would be the formula for something like this?
s=r\theta
$S = r \theta$
soap:
rip me
3pi = 5x?
yep
so 3/5pi = x?
i think so yeah
how do I find an actual value though
wym this is in radians
that's the actual value
so convert pi to 180 degrees i guess
oh i thought the formula was like degrees/360 = rad / 2pi
soap:
$\frac35 rad = \frac35 \frac{180}{\pi}^{\circ}$
soap:
what would these type of questions be called?
geometry....
yeah thats why I posted it here
hi
rectangle
because what you're doing is
you're bisecting a rectangle diagonally
thats how you get the two right trianges
if you put two equilaterals together you get a diamond
or if you switch which side oyu couple them together
you certainly do not get a rectangle```
A triangle has three straight sides ...
so how does
a = bh/2 work for all triangles?
@bleak barn You here?
cos^2(x) = (1 + sin(x))(1 - sin(x))
Guys... Can you help me with this problem?
In the figure below, the triangle ACE is equilateral and the angle DBC = DCB = 20. Calculate the measure of the angle "x".
ok so
In triangle DBC:
angles DBC + angle DCB = 40
so angle BDC is 140°
angle AEC and angle ACE is 60 because equilateral triangle
I wanna do this problem lol
y' = 3cos(x) - sec²(x) = 0
3cos(x) = sec²(x)
cos³(x) = 1/3
cos(x) = 1/∛3
Lovely
Oh wait do you know differentiaton?
bruh arauto that problem is literally ipossible
@winged saddle I saw it in my book... The book says that the answer is 50.. But I really don't know how to discover it...
@glad ocean I'm trying to do that question since morning
wait
In the book does it give any reason why
if not but you really need the hw grade just show work for a wrong answer
uh arauto the problem is angle E and angle D, cuz if u find 1 or the other, u can know ht answer but if u dont find them its impossible
i cant really find a way to find it using traingles, so u should probably set up a system of equations
and try too find x
i mean
try to find
either E or D
@glad ocean Unfortunately my book gives no reason why for it... And I translated the question to english (because It's a book in another language)
@winged saddle Yep.. I was thinking about it.. 🤔 .. That question looks so easy but It's so confuse
@winged saddle
I was thinking of finding X by the external angle theorem, using D and C. Anyway, it did not work out ..
yeah i tried too
im 2 lazy to set up a system of equation so ill just leave it to u LOL
😂
so
you know that one of the angles is 7x and the other is 5x
you know that they both sum up to 90 degrees
solve for that
Do you know why one is 7x and the other is 5x?
exactly so you know that one is 7x and the other is 5x
and they both add up to 90 degrees
therefore x = 7.5, one of them is 37.5 and the other 52.5
Ok I have a question about ratios and area
The question: Two similar wood floors have a scale factor of 4/3. It costs $216 to refinish the smaller wood floor. At this rate, how much would it cost to refinish the larger wood floor?
would you do 4/3=216/X OR 3/4=216/X
can someone help me 😦
sorry i forgot a little bit about scale factors from earlier in the year
so i can't remember which one is right
well dang
I think I have a pretty basic question but I don't seem to be able to google it properly:
I have a point cloud in 3D. I would like to transform these points relative to a given origin. I have the location P and the orthormal basis which I want to use as new.. axes? I just want to construct the translation (mean) and rotation (this one I don't know) matrices for this, if I'm correct?
How do I go about that?
@hardy surge
A translation isn't a linear operation, so matricies can't help. You're better off creating a function. What are you thinking of doing?
Isn't translation one of the affine transformations?
Anyhow, what I need to do is project the given points (already slected) into a 2d subspace (surface). I want to calculate a 2d convex hull of those points.
The easiest way to do this is probably by translating and rotating to the origin so that the forward dimension can be ignored and for X we use object's local right and for Y we use object's up
$|z-1-i| + |z-3-i| \ge 4$
Autistic Hoodie:
I asked my professor and he told me the only way to solve this is using the long claculations
I am trying to do it but it always ends up being incorrect
Or I am missing something...
I got it correctly till this
$6-x \le 2\sqrt{(x-3)^2+(y-1)^2}$
Autistic Hoodie:
Autistic Hoodie:
@hardy surge Look up the affine transformation matrix
It involves augmenting the coordinates with an extra 1, and stripping it off later on.
I'm aware of that one, although I am not sure how to apply it.
Then you can just transform the standard basis, making sure to maintain the 1 on the bottom.
ok so I have 3 direction vectors... that span the orthonormal basis relative to my selected point
but I am not sure... what to do with it... how to apply this.
Lemme explain a bit better
wait that's wrong
Let's just assume that you can find the affine transform of the standard basis.
I believe you actually need 4 vectors, 3 linearly independent, to uniquely determine the affine transformation.
yes, that sounds right. Location and... dimensions
Sorry, my mathematical vocabulary is not that great... especially not in English.
Anyway, you can break the affine transformation into the linear component and the translation component.
The affine part comes from translation.
So, ignoring translation for the moment, you can derive the linear part of the transformation by just transforming the standard basis in your current coordinate system.
Those transformed vectors directly become the columns of the linear part of your transformation matrix, i.e. the A part of the matrix given on Wikipedia.
oooh... I remember this, I think
Then the b is just the translation that you want.
focus on the props of a kite
such as perp diagonals
and one of them perp bisect
and 2 sets of adj congruent sides
@everyone can anyone help me with my prove the given identity homework, im really stuck
the diagram below shows two right angled triangles triangle a is mathematically similar to triangle b the perimiter of A is 12 cm what is the perimiter of B
is the perimiter 60
@upper karma yes
ok ty
np
Substitute known values into distance formula and solve for unknown
What "doesn't work"?
Im so lost its not even funny. Worked 2sin^2(x)-sin(x)-1=0 answers in range of [0,2pi). I got 3pi/2 and pi/2. Answer sheet says pi/2, 7pi/6 and 11pi/6 I have no idea where I went wrong
wait... typing it I see where I screwed up
sup
Is there a formula to order of rotational symmetry for polygons??
@glad falcon Pretty sure that's just the cyclic group of n vertices so the order is n
exercise: The point P' is the refelction of the point P(-1,10) on the line a:x+5y=10 . What's P
like im trying to get the distance of l Pa l with this : lax1+by1+cl / Sqr a2+b2
i end up getting 6 and on geogebra it shows that i should get 7,6....
<@&286206848099549185>
je ne comprends très bien la question. il me semble que le point P est donné, (-1, 10), mais il faut trouver P?
la reflection de P' est P(-1,10) il faut trouver P'
distance de lPal est 7.65
il faut trouver P' , les coordinates
hmmm, moi je commence toujours par dessiner
si vous savez B, vous pouvez trouver la difference entre P et B
:/
(et le français n'est pas ma langue natale... ayez patience svp)
quoi est ton langue natale?
l'anglais
we can speak english if thats easier
mais je préfère pratiquer mon français toutefois
c'est difficile pour moi
tiens, la ligne PB est la ligne perpendiculaire à la ligne donné, et qui contient P
donc si on sait le formule de la ligne donnée, on peut trouver le "slope" (pente?) d'une ligne perpendiculaire
et puis trouver la ligne PB
qui nous donne le point B car c'est l'intersection
et puis on ajoute [la difference entre P et B] à B
vous avez fait l'addition des vecteurs auparavant?
je crois qu'il y ait une méthode très simple que je ne parviens pas à trouver
it's a vector pointing in the direction that the line is going i guess
okay but if we can find B, then we know that to get from P to B you add or subtract some amount from the x-coordinate and a different amount from the y-coordinate
and then you can just do the same thing to get to P'
how do u get B
by finding an equation for the line PB and then finding the intersection of PB and the original line
im like 100% sure theres an easier way
me too
i do know that my method will work but there's probably a trick you can do that shortens the work considerably
watching a vid on ur mtethod
im giving up lol
i have three more of those kind to do
its 11 30 pm
Hey guys
Im@new to this sever, but can you any of you guys help me with this geometry question
maybe
bruh
ok well
since abcd is a square
then ah = dg = cf =eb
ok well thats simple
letss call ah = a
and ae = b
since all of these triangles all congruent, then all of them are ab triangles, therefore, they all have the same hypotnuse, c
so, efgh is a square, because all of its sides are the same length
i dont know what paragraph proof is
sorry
well
for b), since efgh is a square,
a square just has 90 degree angles
so...
not sure y they asked that thas simple ;-;
@silk sequoia
Im trying to simplify and im lost now
Gmsudjeusis
Thanks
Final answer is 1 right?
Also sorta lost on this one, it wants me to factor but im unsure what i ought to factor out
It's immediate once you do that
Im left with sec^2 x - tan^2 x
That should be one of the identities i thini
Final answer is 1 right?
Is this correct?
Im sorry for asking so many questions, ive got a test coming up and ive been having a ton of trouble with these
Looks good to me
Rad thanks
Trig identities are really algebra exercises in disguise. Always try to:
Factor (Difference of squares)
Add fractions together
Those are the common two lol
Thanks :D
I swear there was more than that, I'm drawing a blank
Well, good luck! Feel free to ask if you have anything else
Thanks fam, ill peobably be asking at lwast another 10 times haha
Great! I can't wait
Would #5 be correct? The question is asking what values theta can be while still having the equation be true
Theta is also in between 0 and 2pi
dude fuck I dont wanna do my trig hw this shit gives me aids. all thos identities and shit ahhhhhh
yeah dude second time taking this class and I know I can do decent but like fuck this stuff is so frustrating when u cant have access to a teacher to ask a sumple question. we’re luck we have resources to go to but still fuck me
I dont even wanna think about calculus
or anything above trig haha
I dont have internet access
And i was pretty much surviving off of Khan Academy but cant use that now aha
What u mean bo internet access? u on it now
No wifi at home?
Dickhead father took it away
Grades have plumetted since then but doesnt matter to him at all
Ah I see thats annoying as fuck. tell him u need it to help with homework. im sure u have but he should realize if he’s not dumb.
Beat bis ass
Well goodluck w ya homework Im gonna do mine tomorrow morning I’ll look for ya on here and show u what I got goin.
im graphin as well as the identities lol woooo
Rad
Graphing is kind of a pain in the ass but its pretty much the same as the ordinary shifting rules
@winged saddle all thank you !
your wecloem
What is it?
bruh
my friend is a dick and only sent the problems instead of the equations
yeah it doesnt even say antyihng
I think ur supposed to graph it
bruh
i'll send the other side, it actually has the question on it
Wtf
ok
wow u should have told us earlier
CENTER THE RADIUS
AND GRAPH IT
BRUH
i mena
find the center
and the radius
why are you yelling at me
ok
don't hit me
No he has to write the equation
uh
not graph
just write the equationa nd then graph it
do u know equation of a circle?
no
ok
she started talking about circles and i got scared and turned my ears off
its in the form (x-a)^2 +(y-b)^2 = c
let me explain
c is the radius squared
so if u want to find the raidus
u take sqrt of c
a and b represent the centre of the circle
yes
so if lets say a = 5
then (x-5^2)
oops
i mean
(x-5)^2
x=5
so that it willmake it 0
and u can find y and sketch a point
same thing for y
find hwat valu eof y will make (y-b)^2 == to 0
so
lets take the first problem as an example
ok
on the second page
well
x = 1/2
dog i wasn't here to get this worksheet
so i asked him to send my a photo
his y is good
yeah
x is 1/2 cause it has to equal 0
um i think all the answers are wrong
he did it right for ther adius
lol
bruh
so
and the square root of 9 is 3
ok
for the questions on the first page
u can put the equations into the form (x-a)^2+(y-b)^2=r
and then ssolve for radius and center
etc
there u go
gtg b4 teacher sees me
show me what uve done
Um what question is this
question 7?
oh oh my bad
is fine
shay
ye
And the 9 is the radius squared
becasue there is 2x values for every 1
on the circle right
like if y is 3
then x can be something and something
i can't find any fucking graphing paper and that's an oof
but they are not the same values
so u have to take the square root
to get 2 values
Just draw it
and label the coordinates that are important
Ok so we found the centre of the circle, now we need to find the radius which is the root of 9
shay
Yep so from the centre
for example
lets say y = 0
then there is 2 x values possible
if u only have linear equation
u can only have 1 x value
per 1 y value
if its squared
u can take the square root
u get a positive and a negative answer
so there is 2 answres
and so 2 x values
alright
i dont think i make u understand
you make me understand
but i have to move on, i need to get this done fast
so the radius is
K
So from the centre
u draw 3 out
so the centre is 0.5,2.5
I think u can do that
fuck im shit at explaining
what do u mean the height?
aren't i trying to try and draw out the entire circle?
Ye
yes
the height is the diameter
ok
well
so now u know the center of the circle right
and u just take a compass
and draw it
ye
and u got ur circle

yep
yep
Ok send me a pic of it
i don't have my phone
yep i think i did
night
Look at my name!
u wanna
put it in form
(x-a)^2+(y-b)^2=r
where r is radius squared
so
its kinda mixed up rn
u probably
waanna
group the x terms together
so
u have x^2
mhm
i tihnk it's 8y
to make it a peffect square
it's just hard to see
yes
a long time ago
ok
so
lets say
u have
x^2+8x=0
and u wanna make it
(x+4)^2
=something
u wanna make a perfect square
like in this situation
for the circle
so
wat u wanna do
is make a constant term
understand?
so
what u do is
u divide 8x by 2
u get 4x
and u take the coefficient
which is 4
u square it
it becomes 16
and that is ur constant term
so
look this is what it becomes
x^2+8x+16-16=0
its an equation remember so if u add 16 u gotta substract it
mhm
yes
x+4^2
= 15
i mean
=16
i just moved the 16 to the other side
ok ?
so lets dot hta
for the circle
so
i already did for x
so
now it become
(x+4)^2+y^2+8y+28-16
right
so now u wanna put the ys togehter
yes
same thing
u take the coefficient on the y^1 term
which is 8y
u divide it by 2
4y
u square it
16
and then u have ur constant term for the perfect square
so now it bcome
so it's the same thing for the x that it is for the y
(x+4)^2 +(y+4)^2 +28 -16 -16
well
in this case yes
becuz it is all 1second power term
and 8 for the first power term
but other wise it would be differnt
and then
alright
u have ur equation
so u just simplify for radius
it become
(x+4)^2+(y+4)^2=4
so radius is 2
and center is at -4, -4
there u go
do u have question
ok
if i don't get it i'll @ you
alrigh
Can someone explain me Betwenness in definition?
What about vertical angle theorem?
vertical agnles
In geometry, vertical angles relates to an linear slope on a graph. So if the equation is linear, you can tell because it won't have any exponents.
are u in middle school?
or something
Highschool
Grade 8
but thats not highschool
Wutt.
Nooo
Idk what you are talking about. But I'm not living in US
ok
It's our lesson in 8th Grade
o ok
ABout theorems ;-;
Oh
this
the mesure of angle 1 = angle 3
and the mesure of angel 2 = angel 54
i mean 4
not 54
Wut is that?
it works for any of these lines
like say u have 2 lines
that intersect
like they cross eachotehr
at any point
ok and it will make 4 angles like this:
there
yeah
it is always true
that angle 2 = angle 4
and angle 1 = angle 3
Oh okay
if u add them
If you add 1 and 2 its 180?
Yes
suplementary angles?
Yesss
How did you know that its 180 tho



