#geometry-and-trigonometry
1 messages Ā· Page 73 of 1
this is central arcs and angles my question is when would i use 2pir
i understand the formula theta/360=S/C
but i dont understand when would i use s/2pir=theta/360
this textbook im reading from doesnt really explain it well
Do you know C is the circumference of the circle?
No, $C = 2 \pi r$
Closer
ok circumference =2pir
@kind rapids if i was to just say s/2pir for the first example would that be wrong?
instead of s/c
since c= 2pir
Well, no
But you are trying to compute circumference
So no need to make it to 2pi r
But if you need to compute r then you need to write it as 2pi r
ok so when i need to find radius use 2pir
For example in the first image you can make it to: $2\pi r = 24000$
Closer
And then find r aka radius
ok thank you!
ima have to get a on-campus tutor asap because its only been a week and im alr lost
why is the answer 20? i was thinking 10
this is the answer but isn't that the just the whole area of the flag
are we assuming the flag is a rectangle?
sorry, triangle
the topic is about triangles
but now that you've mentioned it, it may be a rectangular flag, where the diagonal divides it into 2 triangles, which one is of area 20in^2
thanks š
And yea it cant be a triangle as a triangle doesnt have diagonals
good point, i assumed it meant the 90Āŗ angle pointing at the hypotenuse, but it seems i was mistaken, thanks!
Well thatd be an altitude
oh does it? hoepfully i get to that part soon, on the book i'm reading. i'm relearning math from the absolute basics to build a solid foundation before i move to more advanced topics like chemistry, physics, pre-calculus, and hopefully i'll understand calculus intuitively one day š¤£
Kool man
Calc isnt as tough as an high school tchr/ the society makes it out to be anyways
Its rather doable
Good luck though
whatās angle EAD
$\angle BAD= \angle BAE + \angle EAD \
90 = \angle BAE + 60$
olivka
whatās angle BEC then
150
The higher the angle, the larger the opposite side
what does it mean when a function is defined for all R and how do i explain it?
i have two functions, f(x) and g(x) where h(x) = f(g(x)). f(x) and g(x) are both defined for all R
Then h(x) is defined for all R
yes my teacher said i didnt explain it right
and he wants me to explain more lol
he gave me a tip and wrote "is h(x) definition dependent on definition for f" - sry direct translation
wdym
so he asked me if h domain is dependent on f domain since h(x) = f(g(x)). As both f and g are defined for all R. cause i just wrote h is defined for all R
$h(x)=-\frac{3\sin(\pi*\frac{3x}{2})}{4}-1$
delila
Prove Sin^2 + cos^2 = 1 please help me out..
from what definitions?
What defination?
normally we define cos to the the x-coordinate of the unit circle and sin to be the y-coordinate
so applying the Pythagorean theorem directly, cos^2 + sin^2 = 1
1^2 = 1
But image is wrong
howso
cos should me in sin's place and sin should be in cos's place
@obsidian harness
And can you explain the image please
I just explained it
Oh yes
But how can we use pythagoreas here
I am 10th not something like university level
cause we have a right angle between cos and sin
cos is the x-axis
sin is parallel to the y-axis
x- and y-axes are perpendicular
yeah we define it to be the unit circle, so we start out with the circle x^2 + y^2 = 1^2
and then draw cos and sin on the unit circle
Thank you very much mann
Another way is start out with pythogorean theorem
P²+ b² = h²
And divide by h²
Tho this only works for right triangles
But eh in 10th grade thats prolly all youre gonna have to deal with
npnp
also like you know, (opp/hyp)^2 + (adj/hyp)^2 = (opp^2 + adj^2)/hyp^2 = hyp^2 / hyp^2 = 1
by Pythagoras
I'm just introducing the unit circle cause things become simpler if we just let the hypotenuse be 1
and it's useful to do your trig in all 4 quadrants
rather than having to memorise CAST
But like idk if they were introduced to trig the unit circle way in schl
Cuz for me it was all triangles
So yea
I mean yes unit circle is objectively better
I feel they should teach both at the same time
But yea
like say for any triangle we can use SOHCAHTOA, but by similarity we can let hyp = 1
I mean the circle covers the triangle part anyways, but the vice versa is not true
cause trig ratios aren't affected in similar shapes
I thought they teach trig in terms of triangles first and then to the unit circle
Yea thats what happened for me at least
they do
but unit circle is just good
Yea its better objectively
i was happy to visualize trig with unit circle
when i was taught trig
than i was with triangles
whats the difference between range and codomain? i wrote two different things on them but still got wrong š¦
I think they are the same?
oh my teacher replied and said that they in general dont have to be the same? š«£
the range, which you should refer to as the image, is a subset of the codomain
for example, if I have $y = x^2$ where $x, y \in \mathbb R$
south
the codomain is R
yeah
question
so is
[-1, 1] range then?
he said i had written basically the same on both
for which function?
yeah
yeah the range for the above one is smtn else
ohh ok idk he just wrote i had done the same on both
yeah the codomain can be defined as anything, although a natural choice for the codomain is all real numbers
cause i had defined the function for all R and then for range i wrote tht
yeah
this is the range for the function above
to properly define a function you need 3 things:
- the domain
- the codomain
- the relation between the domain and codomain, the function 'rule'
at high school level we assume that 1) and 2) are all real numbers unless specified otherwise
ye
not many high schools teach Diophantine equations
those are the solutions to ax + by = c if x, y are now integers
ohh i see
so yeah 1) and 2) are important, just make a mental note of that
thanks so much
np
also would u like to help me define function h heh D:
if u have time otherwise its ok
I can't, thanks for asking tho
Whats the point of taking sin and cos as y axis and x axis respectively and solving through Pythagoreous If we already knew that its hypo is 1.
Why should we consider hypo as its answer as 1?
Please help out with this
<@&286206848099549185>
you already know the hypotenuse is 1, and then using the unit circle you can see that cos(theta) and sin(theta) is defined to be the sides of the right triange. Thus, for any angle, sin^2(theta) + cos^2(theta) = the hypotenuse, and since you know the hypotenuse is 1 since it is a unit circle you know sin^2(theta) + cos^2(theta) = 1
does anyone know the actual name of a cubic Torus(ring shape)??? im going crazy as it does not have a name
Maybe 30?
Yes
Lie on the same flat surface
we already answered this
when
60
whats another way to express DAE
I need more help
do i need to memorize trigonometric identities or can i just figure them out during my test
Hello, could anyone explain to me how Iām supposed to solve number 15. I already tried a few things but Iām getting the wrong answer still.
you have b/c = sin(β)
Using trig it's 2 * arctan(1/(sqrt3 + 2))
If M is the midpoint of DE, we want DM and AM
Let DM = 1 so the height of the square is 2
Then the height of the triangle will be sqrt3
So that arctan is angle DAM and we multiply it by 2
It depends on how quickly you can derive them and how much time you have
i don't like this
,w 2d distance formula
$\operatorname{dist}(a, b) = \sqrt{(x_a - x_b)^2 + (y_a - y_b)^2}$
CyclicTree
this 4 times (or 2 if you are lazy) gives perimeter
,w gauss shoelace formula
$2A = (x_1 y_2 - x_2 y_1) + (x_2 y_3 - x_3 y_2) + \ldots + (x_n y_1 - y_n x_1)$
CyclicTree
gives area
or you can find the height. or you can also use law of cosines or cross product or determinant or whatever else
mixed up opposite and adjacent woops
how do I get there aswell
there has to be a simpler solution than using trig
oh wait I got it
CD = CB = CA cause ABC is equilateral, so triangle CDA is isosceles
so angle CAD = (180 - 90 - 60)/2 = 15
by symmetry, angle EAB = 15
so angle CAD + angle DAE + angle EAB = 60 and hence 15 + angle DAE + 15 = 60
DAE = 30
ok
why don't you try drawing it yourself
i am having a bit of trouble with that
ok, with which part exactly?
now you're blaming me?
if you can go slower that would be fine
no sorry im am not
I just wanted you to help me a bit with the drawing thats it
is that fine for you, then I would nmot disturb you any longer
is this better then
I guess what I wrote isn't sinking in for you
and I don't think me speaking more will help
I literally cant find it
I found the perimeter but not the area
I used the distance formula
Here's an idea
You see how the x axis splits it into two triangles?
Since parallelograms have opposite sides equal, you can cut off top triangle and move its long side to match the long side of the bottom triangle
but then you still have the slanted bit on the right
which you can again cut off and move to the left
now you have a 5x17 rectangle
so the area is 5*17
In geometry, an inscribed planar shape or solid is one that is enclosed by and "fits snugly" inside another geometric shape or solid. To say that "figure F is inscribed in figure G" means precisely the same thing as "figure G is circumscribed about figure F". A circle or ellipse inscribed in a convex polygon (or a sphere or ellipsoid inscribed i...
According to conventions then is it alright to call a circle āinscribedā in a rectangle?
cuz it doesnāt touch all its edge and can at most touch 3
It can touch all of them though?
i mean yes obviously
A square is just a special kind of rectangle
either 2 or at most 3
So i dont get what you mean
if itās a square then 4
It can touch all 4
iām asking about the definition of inscribed
and whether it allows shapes like this which isnāt ātangentā to all sides
Yea if it doesnt touch all the sides then its not inscribed simple as that
where in the wiki does it say that
because i think this has to do with definitions
and conventions
To say that "figure F is inscribed in figure G" means precisely the same thing as "figure G is circumscribed about figure F"
Iguess so
But idk how this will extend to circles
Yeah but if u search ācircle inscribed in rectangleā u see our case
i need a definitive answer on what the convention is
I mean this kinda means that?
But what even is a vertex in the case of a circle
Tho there definitely doesnt lie one on the 4th side
So yea
thatās different
thatās talking about inscribing a polygon in a circle
How so
check the sentence before that
It clearly says the outer figure is a polygon so?
no
A circle or ellipse inscribed in a convex polygon (or a sphere or ellipsoid inscribed in a convex polyhedron) is tangent to every side or face of the outer figure (but see Inscribed sphere for semantic variants).
They are not really related according to me
this sentence answers it
youāre looking at the next
which is the āoppositeā
as in, itās circumscribed now not inscribed
Nvm why th did i miss that sorry for wasting your time
30?
Basically join AD and AE
And ACD and ABE (the two new triangles) are isoceless
Soo BAE = BEA
And we also know ABE =ABC+CBE =90+60 =150
So now you can find BAE and CAD
Also CAB = 60 = CAD +DAE + BAE
what does the second point mean
DI = FI = EI
the circle is tangent to each side yeah
thanks
ender already provided u a solution, but if u wanted another one:
if you can show <CAN = <BAK = 15 then you're done
how
how do you know these are equal
I have the same exact question
this one is good tho
help
Prove sec
DCB = 90°, BCA = 60° -> DCA = 150°.
CB = DC, CB = CA -> CD = CA -> CDA = CAD.
DCA + CDA + CAD = 180°, CDA = CAD -> DCA + 2CAD = 180°.
DCA = 150°, DCA + 2CAD = 180° -> 150° + 2CAD = 180° -> 2CAD = 30° -> CAD = 15°.
Symmetrically, BAE = 15°.
ABC - equilateral -> CAB = 60°.
CAD + DAE + EAB = CAB, CAB = 60°, CAD = BAE = 15° -> 15° + DAE + 15° = 60° -> DAE = 30°
Prove sec^2 = 1+ tan^2
what's sec?
sec(x) = 1/cos(x)
sec²(x) = 1/cos²(x)
tan(x) = sin(x)/cos(x)
1+tan²(x) = 1 + sin²(x)/cos²(x) = cos²(x)/cos²(x) + sin²(x)/cos²(x) = (cos²(x) + sin²(x))/cos²(x) = 1/cos²(x)
theyāre similar triangles
also C(red) = B(red)
problem 1: recall that a 45-45-90 triangle has sides 1 : 1 : sqrt(2)
so what must you have to get ? : ? : x, if the hypotenuse is x
once you figure out what ? is, ? + x + ? = 2 so you have an equation in x you can solve
for problem 2 you can consider triangle formed by centers of 3 smaller circles
and then find the distance from its center to one of the vertices
that +a gives you radius of the bigger circle
it's the same deal with problem 2
the middle triangle is equilateral cause all the sides have length 2a
so you can use trig to figure out what ?, the distance to the centre of the big circle and the centre of the equilateral triangle, must be
sine rule for example
or right angled trig
I appreciate the help but can you please make it clearer?
what could I make clearer?
I didn't really get the terms you used to represent it
ok thanks that made it clearer
can I also ask how to get the sides of the triangle with only angles?
it's a 45-90-45 triangle so you could use trig if you wanted to think about it that way
so x cos 45 or x sin 45 would both work
ok thanks
if my function is supposedly surjective, the codomain and range is the same?
Yes
$[-\frac{7}{4}, -\frac{1}{4}]$ so this is codomain and range?
delila
For what function
$h(x)=-\frac{3\sin(\pi*\frac{3x}{2})}{4}-1$
delila
So the range would be this
ya
The codomain would normally be part of the data of the function
In this case it could be any set containing the range
oh how do i
So, the codomain would normal be given to you, and itās not really something you can deduce from just a formula
The range/image is, though, so long as you know the domain
yeah
my teacher said i got the codomain right but explanation wrong
for why domain is R and codomain
can anyone help me to find that angle??
DAO is coming out to be 80 ig and DEC is 60
thanks bro
Solve x^2 + x + 1
There is find roots
,w x^2 + x + 1 find roots
quadratic formula or the factorison of x^3 = 1 and thus x^3-1 = 0 gives that
im having trouble with this problem, i cant find any remotely nice expression for this line
i got y = -x(2ca/(-2b + a))/a + 2ca/(-2b + a) but i feel like theres a better one
You could multiply both sides by (-2b + a) but that is the best we can do i guess
it seems that you already did this, but you can use the fact that any two sides added up should be greater than the third side
I thought it was a question on Pythagora's theorem
Even though the 90° angle isn' marked with the usual little square š¤
Noā¦.
Iām aware
How could I find an acute angle theta if itās arcsin or arccos
Problem 33
Nvm I got it
lol
If $\cot \theta =- \frac{7}{2}$ and $\cos \theta > 0$, is $\tan \theta= -\frac{2}{7}$?
Primordial
Hello, im doing hw on Trig equations, and im confused on how to get multiple solutions, I was able to figure out 1 solution to this problem, but not for the other ones
would point H be considered coplanar and why
Yeah ig, why will it be not??
I am getting total 4 distinct solutions of t --> cos t = 0 gives t = Ļ/2,3Ļ/2 and cos t = 3/4 gives t = 40,320(approx), are these the solutions?
coplanar to what?
If the question is as you stated, then the answer is "no, because you can't talk about an individual point being coplanar"
Thats #calculus
(Find slope of the tangents then use that to find to slope of the normal and we also know the point)
Guys, for question B does the domain after being manipulated become -10pi/3,x,8pi/3. I multiplied by 3 first then minused pi/3
Nani
like yes the domain for "3x-pi/3" sure
you manipulate the interval domain
-3pi <= 3x <= 3pi
so -10pi/3 <= 3x-pi/3 <= 8pi/3
its hard to check this, but you can do one thing, just apply the general solution of cos Īø which is --> Īø = 2nĻ Ā± α, where α ā (0, Ļ], here is alpha is any solution in the given range(for example in your case alpha would be Ļ/3) and n is set of integers, from this you can easily put values of n that gives you the values in [-10Ļ/3, 8Ļ/3]
then solve for x
tips how to study basic trig fast im in alg2 and have a math comp with it soon
When converting from rectangular to polar, how do you know whether you should add 2pi, add pi, or not add anything at all? Because on some of these answers it tells you to only do one of them or either
you should plot the point on the xy-plane to figure it out
so (-2, 1) is in the 2nd quadrant, so it would be pi - arctan(1/2) which is equivalent
the rule for arctan is that it always gives you an angle in the 1st or 4th quadrant
1st quadrant gives you a positive angle and 4th quadrant gives you a negative angle
so for the 3rd quadrant, add pi radians
for the 2nd quadrant, also add pi radians
for the 4th quadrant, you want the same position but you want to make it positive, so you add 2pi
but instead of thinking about this as a list of rules, just plot the point and remember this
Alrr so basically we'd add pi or 2 pi, to find the other solution? And i'm guessing that the 2nd question didn't need to be added. because it's already in a positive coordinate?
correct, (2, 4) is in the 1st quadrant, so we don't need to do anything
I see I see
What's wrong with having negative values tho?
I get if you were measuring something you don't want a negative value, cause that jus makes no sense.
But in a case like this, why change it to a positive, if you got sum from the 4th quadrant?
there's nothing wrong, it's just that the question specifies $0 \le \theta < 2 \pi$
south
that's the domain we usually use for angles
OHHHHHH
Omfg I can't believe I missed that š
That shi always gets me, whenever their's an interval
*there's
Thank you for helping tho š
nw!
@everyone@here
- Guys can anyone pls tell me that what is an arc in geometry?
- Guys can anyone pls tell me that what is pi maths?
i need help with this
3sinA+5cosB=3
3cosA+5sinB=7
Find cot(a+b)
Pls help
I got Final exam tomorrow
sin^2 + cos^2 = 1 right
now divide everything by cos^2
don't ping everyone and here, they don't work
also you can Google the answers to your 2 questions
find $\tan(a + b)$ first, so you can actually find $\sin(a + b)$ first
south
square both of your simultaneous equations and add them together
you get $9 + 25 + 30 \sin a \cos b + 30 \cos a \sin b = 3^2 + 7^2 = 58$
south
so use the Pythagorean identity to find cos(a + b)
great, now you have tan(a + b), then take the reciprocal of what you have to get cot(a + b)
have you tried using the double angle identities for sin 2x on the LHS?
you should know how to express sin theta and cos theta in terms of tan theta at this stage
yeah on LHS i got some long term
but ig i did it?
Is it okay if someone checks my answers on this review paper?
The problem is that, I jus wrote my answers and did the work on paper
Help
anywhere in particular you find yourself lost?
ok
the first step is listing the equivelences based on what tan is
then, they solve both equations for y
so she just left off the "y="?
so she set the both equal to eachother and simplified
where did the x in the right half of the equation go
oh
thats why its minus
no
idk
$x \tan(63)- x \tan (53) \rightarrow x(\tan(63) - \tan (53))$
OH
KirbysGames
and then she divided
yep!
tan63=y/417 ?
yep
omg
then solve y
you're good, we all have those moments lol.
and you're welcome
have a great night
I got a doubt in circles
ask
Why's there 2/3 ad= 2/3 BC and so on
the centroid is always 2/3 of the way between a vertex and the midpoint of the opposite side
EM:DC = 1:2
so by similar triangles, EG:GC = 1:2
similarly for the other sides
cause it doesn't matter which points you label as A, B, C
Thankz
450
if you don't show your work this is what happens
you get ignored or someone just gives you the answer
without the solution
and don't expect people to give you a solution cause you could have pasted this question here in 2 secs and just left
without doing anything else
i had solved this question in the morning
Everyones willing to put just as much effort as you at max
just ask your q
idk man
no one wants to do JEE stuff if it's not their homework
I actually like doing JEE stuff but I dislike pure geometry and 3d stuff,conics pretty good
Everyone does
Yeah if,it's pretty common, whoever I ask has the same opinion except some exceptions here and there
Btw which grade you in @fringe perch
12
Noicee
But it's the one of the easiest chapters which fetches you marks
Yeah ik
Hm
Perimeter is all the sides added up
SO I SET ALL THE EQUATION TO 20?
NO
ARE YOU TAKING A TEST?
NO BRUH
Oh it's just practice
I wouldnāt be able to use my
Phone
So can you help me
Gimme a few mins
Equate ad with bc , and ab with dc
It still gets messy
Yes it would
I got 71/9
Photo math said 7
IDK
It's 7
Trust photomath fr
Sry 7
HOW DO I FIND IT
One sec
OKK
Wait photmath is wrong
Are you guys searching it up
Possibly (No)
Hell nah
@oblique widget here u go
Got it?
Let me look
Nope
Where did the 2 come
From
Ok
Which one?
The first step distributive property
You see 2l +2b= perimeter
Why is it l and b
Take the 2 out as common
I have different variables
Oh
You wrote wrong
I DONT UNDERSTAND
We use different variables here
this problem is dumb
Yes
I didn't solve for each individual variable
And i took 3 minutes to solve it
My teacher didnāt even teach this
What i did was make x=(w+3)/2
But
I give up
Everytime I do the problem over, I get different values for x and y
Yeah
What is it?
@oblique widget
What is it?
Verbally?
Like text
Ask someone else , I'm not good at English!
Wait then
Donāt write it on paper just like tell me step by step
Gimme 5 ninutes il
And I write as u say
Can I get the digital copy of that question pls!
@oblique widget where have you gone?
Uh whag do you mean digital
Iām doing my work
First let's take ad as l
And ab as b
We know that 2(Ab+Ad) =22
Ab +ad =11?
@oblique widget
Ok
So you could apply the value of ab and ad in the equation we got
You'll get
2y+1+3x-2=11
Solve this
@oblique widget
Did you get it?
One sec
Oh sorry I can just do it myself then
Wait Ill finish it off and go
You'll get 2y+3x =12
Upon using ur brain
Just plug some random values and see if it's equal to 12
If u plug in x as 2 and y as 3
Youll get 12?
So we can conclude that y =3
Line ab =2y +1
=7
Any queries?
@oblique widget
Ok
I tried but got an error
It said sonething like
Error 404 brain not found
You need medical attention
Fr
Its looks grey
How do u know if you don't have one?
Everything is grey
You grey me grey everything grey
Grey everywhere
What grade
Hey friends is there any way I can complete straight lines chapter in one day?
I have my maths exam in 10 days and I am cooked
⢠Basic concepts of Points and their
coordinates.
⢠The straight line
- Slope or gradient of a line.
- Angle between two lines.
- Condition of perpendicularity and
parallelism. - Various forms of equation of lines.
- Slope intercept form.
- Two-point slope form.
- Intercept form.
- Perpendicular /normal form.
- General equation of a line.
- Distance of a point from a line.
- Distance between parallel lines.
- Equation of lines bisecting the angle
between two lines. - Equation of family of lines
- Definition of a locus.
- Equation of a locus.
This is the syllabus
Yes :D
Are you starting from the beginning or you have previous/some knowledge of it?
Morning (3-4 hours):
Basics First
Points and Coordinates: Just do a quick brush-up here, maybe 30 mins tops.
The Straight Line:
Slope/Gradient (30 mins) ā get how to calculate and why it matters.
Angle Between Two Lines (30 mins) ā learn the formula and maybe run through a few examples.
Perpendicularity and Parallelism (30 mins) ā focus on those conditions.
Line Equations (1-1.5 hours):
Cover all the forms: slope-intercept, two-point, intercept, perpendicular/normal, and general form. Make sure you can convert between them smoothly.
Afternoon (3-4 hours): Application TimeDistance Problems (1.5 hours):
Point to Line Distance (45 mins) ā know the formula and practice.
Distance Between Parallel Lines (45 mins) ā same deal, understand then practice.
Advanced Line Stuff (1.5 hours):
Equation for Lines Bisecting Angles (45 mins) ā get the concept and practice.
Family of Lines (45 mins) ā focus on deriving and using the equations.
Evening (2-3 hours):
Locus and Review
Locus Problems (1.5 hours):
Definition + Equation (1 hour) ā dive into understanding and deriving equations.
Quick Review + Practice (30 mins) ā hit the key points again and do a few problems.
Final Hour: Recap & Test urself:
Go over formulas and concepts quickly. Do some mixed problems to see where you're at.
Well.. i indeed have nothing to do if i wrote all of this
bro prepared a time table

I am NOT spending an hour and a half on line equations
use the alternate segment theorem
hence AC is the diameter of the circle
the diameter makes an angle of 90 degrees to both of the tangents
hence proven
by angles in the same segment, it doesn't matter where point D is
Ok I must have forgotten some properties of parallel lines
no you forgot your circle theorems
How does the diameter making 90 w the lines tell us there parallel
And wasnāt that the diameter making 90,s alr given
so if line l is perpendicular to the diameter, and m is also perpendicular to the diameter
lines l and m must be parallel
Or can we not assume that
no you need to show that
I mean if the angles were different, you could have something like
Ig this would make sense for like alternate interior and all that
actually there's an even simpler way that I overlooked cause I thought it was assuming the q
Dang I gotta stop assuming stuff
draw a parallel line to line l through point B
oh wait I think that's assuming what we want to prove
I was trying to make a line through b and show that l and m are parallel to that so then l and m are parallel but it didnāt work
yeah I think you actually need this
yeah I thought of that too, draw a perpendicular line to line l through point B
the problem is that you can't show that the two perpendiculars coincide
so you haven't shown you have a straight line through B
btw I found AOPS's solution
no worries
Yea I have the solution manual you just made me realize tho that the AC is the transversal and that we had to prove itās a str8 line
How to prove $\sin^{2}A + \sin^{2}B - \sin^{2}C = 2 \sin{A}\sin{B}\cos{C}$
KingDanger
Approach Zero: A math-aware search engine.
approach0 is goated
hah I was thinking of the circumscribed radius approach
and someone answered, slick proof
Why the hell did you not write the given condition
it felt like something was missing
What is circumscribed radius approach?
so $\sin A = \frac{a}{2R}, \sin B = \frac{b}{2R}$
south
Sry
I have the topic law of sines and cosines in my later topics but now I want to solve this with sum or product and conditions
Previous knowledge I have
ez
how do you get the first step
They are half angle properties taught in trig
Do you want like the derivation?
Cuz its pretty doable use sin4x = 2 sin2x cos2x
Now try to express this in terms of only tan
Similarly you can do cos
yeah
im stuck with a stray cos^2 2a at some random point
Write it as 1/sec^2 2a
I need help with the one marked with H
Basically they gave you a circle and and two legs of an inscribed triangle and theyāre asking you to find the third
Yep I did it
Nice
does anyone know what the Sc on question e represent?
I need help with this question, your supposed to use this format to find the answer: y=ax+b
so, first we know one point is on (-1,2) and the other on (3,5)
the slope of a line that connects these two points are (5-2)/(3-(-1))
=3/4
thus, a, which represents the slope, is 3/4
to find the b, we can replace y with (y-y_1) and x with (x-x_1)
(y_1 and x_1 are the coordinates of one of the two given points, although any point on the line works)
for this solution, i'll use (3,5)
so, y-5=(3/4)(x-3)
expand this to get
y-5=(3/4)x-9/4
add 5 on both sides to get the final equation
y=(3/4)x+11/4
i should learn how to use the latex bot
yeah that also works
as far as i know, there are a lot of methods but all of them involve using the two points to find the slope and then one to find the y intercept
(at least all the methods i know)
the number 5
i don't believe this goes here
but sure
in an arithmetic sequence, given a term aā (where n is not 1), aāāā=aā-d and aāāā=aā+d
aāāā+aāāā = 2aā-d+d = 2aā
Thus, 7x-1+6x-9 = 2*8 = 16
13x-10=16
13x=26, x=2
Therefore,
8x+2=18
7x-1=13
8
6x-9=3
late reply (and thus ping)
but i believe S represents the sample space (i. e. the set of all possible otucomes)
<@&268886789983436800> spam link
Hello
hi
thank you
Hello
How do you reflect shapes over a diagonal line?
Isnāt it just sequence a
If you rotate it 270 degrees, isn't Point I to the right of J?
Yeah your right itās sequence b
I was confused on where the origin was
How did you reflect the shape over HI?
I'm confused as to how to do diagonal reflections.
I just did the individual points
So like this (roughly)?
Yeah
Iām honestly a little confused so I just went to the points
Then the rest is self explanatory
It looks kind of like a 90-degree rotation.
I saw it like that yeah
just gonna say this
the reflection does seem similar to a rotation, but without some sort of symmetry, it is impossible to have two congruent shapes be able to overlap perfectly using only rotation if one is a reflection of the other
just to clarify
cannot be 90 degree
NOO
LOOK!
ITS REFLECTION
MAKE THE LINE PERPENDICUILAr
THEN SAME DISTENCE ON THE OTEHR SIDE
let's reflect a point with respect to a line
first, we find the foot of perpendicular from P to l
the distance is d
extend the line segment by d
the end point is P' (the reflection of P)
now, other shapes are just a set of points
shapes can be reflected like this
for polygons, or angled straight lines, reflect each vertex and then connect the corresponding points
for other shapes like circles which only require a little information, reflect specific necessary points (like the center of a circle) and use the information from earlier to draw the shape
applying it here,
(assuming the side length of a grid square is 1)
Thank you so much! This was really clear.
So it's just two points that are equidistant from each other.
Im not tripping right? This is correct?
Brooo, why'd my teacher doc me šš
what the fart why did nobody help me
the graph shows the three possible pointsfor the triangle to be half of a parallelogram
How abt problems like these? Cause doesn't the sin and sin-1 cancel?
Which jus leaves the degree
Yeah -pi/2<Ćø<pi/2
because sin is a periodic function, different angles can have the same sine value
So it would jus be sqrt(2)/2
-225 degrees is smaller than -pi/2 radians
which means the value of a sin^-1 function can never be -225 degrees
(or its equivalent in radians)
Yeah so we would have to find a degree that's the same value as -225ā° and between this interval
Right?
yes exactly
Which would be -60ā°
Wait your right mb mb šš
dw that happens
There was one like this to that said cos(cos-1 (5))
But that would be undefined, right?
5?
yeah i think that's undefined
Yeah I got it wrong cause at the time I thought the cos would cancel
But I woulda had to say "undefined"
Yeah I fell for hella on this section
Like on this one, tbh I had no clue what to do, but I saw cos/sin and immediately thought of Cot(10) š
oh
But I think you were supposed to apply the complementary angle formula
Idk when to apply those tbh
when you are given two values to operate with
if the two values add up to 90+360n degrees (or 270+360n) you can assume you might need to use it later on
(i believe you do have to take the signs in account for 270)
I see I see
sin(Īø)=cos(90-Īø)
sin(Īø)=-cos(270-Īø)
I thought this problem you'd have to apply the complementary formula š
oh
Or I think you do, but I somehow forgot abt the sin
the last question?(question g)
The one is cos(90-22.5)
oh
Yeah
that one doesn't 'work' because neither 22.5 nor 67.5 are the special angles
Oh wrrd they have to be a special angle š
you have to use the half-angle formula of cosine from cos(45)
either that or
draw a triangle
What šš
How do yk when to apply thaf šš
when you get angles that aren't 0, 30, 45, 60, 90
(or +90n variants of them)
you have a few options
if the target angle can be split into 2 of the special angles
such as 75 degrees (30+45), you use the addition formula
if the target angle is half of a special angle such as 15 degrees or 22.5 degrees (half of 30 and 45, respectively), you use the half angle formula
of course, this only applies to numerical values of the angle, if it's given as a variable like Īø, you have to use a different approach for each scenario
when learning about formulas and such, it's a good idea to learn or think about what scenario you want to use them in
Shi I see I see
I didn't think this test would have us apply any sort of formulas on this section
Thought it would jus be common angles and finding the values šš
So is this how you would show the work for this problem?
This means that we would have had to apply the sum or difference formula
On this question
Omg
I'm pissed šš
I sold this test
Their were other problems that I screwed up on aswell, but that's because I wrote the wrong values from the unit circle š
Oh yeah fs
I knew I shoulda wrote the values on the unit circle that my teacher gave us š
Should i ask if I could retake šš
Couldn't hurt to ask, right?
don't know about that myself tbh
i only know geometry and a bunch of other miscellaneous stuff
Fair
but if you think you should, go for it
Alr I might. I got a couple more, How abt these couple of questions?
i don't get how you did the first question
considering the value of β isn't shown
now, i don't know exactly what the paper means by 'direction'
but the magnitude is just pythagoras applied to 7 and 3
for question 5a, that's just arithmetic
if the direction means the direction relative to the positive x axis, the direction of the Q4 would just be tan^-1(3/7)
the angle between the Q5 vectors u and v is given by the formula
cosĪø=(uā
v)/(|u||v|)
where uā v is the inner product of u and v
Oh yeah mb
Their was multiple parts in this section, with using the same cos and sin
Yeah I realized that after relooking it. But direction is finding the angle which at the time I think I didn't for some didn't see that portion of the question, and didnt do it
Oh shi, so the dot product?
yeah
I thought all you had to apply was tan
tan theta = y/x only works when you have one vector and you want to find the angle with the x-axis
the intended method is to find cos theta using the dot product then use the Pythagorean identity / draw a right triangle to find tan theta
seeing that the angles are approximate (at least from what i can see)
i think just getting two tan^-1 values and subtracting them should work
there are definitely other methods too
But since we're working w 2 vectors it doesn't work
if you draw it out, you have that v is in the first quadrant and u is in the fourth quadrant
so $\theta = \arctan \frac{2}{3} + \arctan \frac{3}{4}$
$\tan \theta = \frac{2/3 + 3/4}{1 - (2/3)(3/4)}$
it works if you think more creatively
answer to question b is wrong, the value you got is higher than 1
oh wait it's 3/4
south
root3 COT^2 - 4COTA + root 3
Guys please help me in solving theis
this
stop spamming
also you want this equal to 0 right?
No, COT^2 + TAN^2 = ?
there's no identity for that
you also didn't answer my question regarding this
root3 COT^2 - 4COTA + root 3
then COT^2 + TAN^2 = ?
Guys please help me in solving theis
this
