#geometry-and-trigonometry
1 messages Ā· Page 276 of 1
oh sorry.
I have R=a/2sinA
But they want me to express it in terms of let's say a b and sinC
And S=abc/4R comes after I show that S=1/2.bcsinA and R=a/2sinA, it's not shown yet and I don't think it gonna help
I think there's something wrong in the question idk why
S can be expressed the way they asked
And R the simplest form of it is a/2sinA
I tried to use vector product
I got ab=R^2.|1-|sinA|-|sinB|+|sinC|| or something like that
I even said R=a/2sinA=b/2sinB
So R^2=ab/4sinAsinB
Used some trigonometric formulas
But didn't get anywhere
Maybe I missed something or the question is wrong
I never encountered a simple expressing of R in the form they're asking for
Is there someone I can dm about proving trig identities.
I do not want to cut in on the problem being worked on here atm
rewrite tanx and secx in terms of sinx and cosx
So focus on the left side, not right
you can do either but left side looks easier
https://gyazo.com/1adb1fd3ce458bf2ac67a0e3465d4953 so if I have this then cos(63) = 23/x and i forgot how to find x pls help
do the same stuff to both sides of the equation to work towards isolating x
divide by 23?
use trig
that may help depending on what you do afterwards
oh wait you did
cos(63)/23 = 1/x
(if you meant dividing both sides by 23)
now im stuck
dont divide by 23
Now take the reciprocal
you could take the reciprocal of both sides
i forgot wat that means
You can do this because the reciprocal function is injective
wait so just cos(63)*23 = x
no
probs better to approach it another way
from cos(63°) = 23/x
consider first multiplying both sides by x
well honestly i can probably just guess from the asnwer choices i have
don't guess
It is.
can someone draw this for me
i drew it incorrectly
and got wrong answer
i cant imagine it
@gritty sail use geogebra
how do i make it 3d @rich wolf
nvm i found it
uh nothing shows up
idk how to use
it doesnt work
i did
?
!
@upper karma use the section of a circle formula or derive it from the circle one
Hi, how do i calculate x and y axis of a triangle if i know that the hypotenuse is 10 meters and the x and y is in a different coordinate system. How do i convert x and y to be in the same coordinate system as the hypotenuse.
you mean in a different measurement system?
i.e. that the legs are 0.3 and 0.2 respectively of an unknown length unit?
ye
well
letting x be the length of this unknown length unit in meters
you have $(0.3x)^2 + (0.2x)^2 = 10^2$
Ann:
ye
well
how do i get x, long time ago i did this kind of stuff š
Find, in radians, the acute angle for which $\frac{1}{(1+cosec\theta)(sec\theta-tan\theta)}=3cot\theta$
Hmm:
fucking shit i overcomplicated it for myself now im stuck š
ping me if u wanna help
"put things in terms of cos and sin" means "put things in terms of cos and sin"
and then perhaps do some algebra to get rid of the skyscraper fractions
lets see
i got rid of the fraction
cuz
1/sec
all that
thats what i meant
@dark sparrow
idk what im doing
hhf wow you
overcomplicated it way too much
gonna replace $\theta$ with $x$ for simplicity:
$\frac{1}{(1 + \frac{1}{\sin(x)})(\frac{1}{\cos(x)} - \frac{\sin(x)}{\cos(x)})} = \frac{3\cos(x)}{\sin(x)} \ \frac{\sin(x)\cos(x)}{(\sin(x) + 1)(1 - \sin(x))} = \frac{3\cos(x)}{\sin(x)} \ \frac{\sin(x)\cos(x)}{1 - \sin^2(x)} = \frac{3\cos(x)}{\sin(x)} \ \frac{\sin(x)\cos(x)}{\cos^2(x)} = \frac{3\cos(x)}{\sin(x)} \ \tan(x) = 3\cot(x) \ \tan^2(x) = 3 \ \tan(x) = \sqrt{3} \ x = \pi/3$
Ann:
how do i find area of equilateral triangle with side x meters and 60 dergrees
do i use $\frac{1}{2}ab sin c$
Hmm:
Sure
i did it anyway
\sin
how can i use the sum to product formula on $a\sin(\alpha)-b\sin(\beta)$?
nix:
can you give more context on your question?
https://gyazo.com/1613123cd359dc385a9888285fede9dc im confused on which angle it is asking for
The right one if im not wrong
ok
of course
Ok good
@thorn grotto I just want to know if its possible to use a trig identity to write that sum as a product
can anyone help me with "Determine the exact value of the trigonometric functions. cosin210"
do i literally just do cosin 210?
(in deg)
ok i didnt think so
210 is also 7pi/6 radians
i watch tutorial videos and it always brings that up
but how does that help me? they always explain it in a way i have a hard time understanding in
let me see if i can explain which part i dont understand
can someone help with my q i still cant get it
thank you @glacial haven
Jbao I'd like to help, but it's hard to explain without proper drawing tools
Does this help?
Random Tip: trig formulas based on the unit circle for complex numbers. (less memorization or a way to check your memorized formulas)
z1 = cos(A) + isin(A)
z2 = cos(B) + isin(B)
z1 * z2 = (cos(A)cos(B) - sin(A)sin(B)) + i(sin(A)cos(B) + sin(B)cos(A)) = cos(A+B) + isin(A+B)
A = B
z1 * z2 = (cos^2(A) - sin^2(A)) + i(2sin(A)cos(A)) = cos(2A) + isin(2A)
C = 2A
cos(2A) = 1 - 2sin^2(A)
cos(C) = 1 - 2sin^2(C/2)
sin(C/2) = +/- sqrt((1 - cos(C))/2)
... and others.
oh wait that said floor function! I thought that was absolute value symbol! @dusky surge thanks!
@surreal bolt yeah I saw that in 3blue1brown quaranteen video
i would assume isosceles triangle
what
then use pythagorean theorem, then cosine law
i srsly have no clue what im doing
assuming that's a isoceles triangle, you can split it into two right triangles, sides with 1.3 and 1.8
okay
then you can find the third side with pythagorean theorem
wait.
you don't need to do that
hmm
do you understand what you are doing
basically we are splitting the isoceles into 2 right triangles
does that part make sense
ye i got it now
How do I write the equation for this?
@tender iron do you know the equation of a circle?
no
Look it up on google
I have the equation formula - I don't understand how to fill it in
try messing with desmos.com until you get it right, and also understand why it is right.
(x-b)^2+(y-c)^2=r^2
Oh yes
b and c are the points at the center
Also to clarify, they want you to express that formula in x and y terms, so:
(x-"number")^2+(y-"number")^2=number²
alright ty
Np
@spark lintel here
ok
tan(2x)=2tan(x)/(1-tan²(x))
Yeah
what about sec2x?
Al3dium:
Yeah
and the tan
Yeah
are they subtracting each other?
Yes
One sec
cos²x + sin²x
Can anyone help me with a question that has been stumping people
oof
Yeah try
Not sure how
Look
Tan²x=sin²x/cos²x
Put it tan²x
After done that, do common denominator with 1
Lmk when you are done
With that
@spark lintel
š
one sec
Sure
Not sure what you did
Take them away from the paper it'll look easier
Like this
Do common denominator on:
$1-\frac{sin²x}{cos²x}$
Al3dium:
Imagine this a separate exercise
If you cant still get it, do it simpler, common denominator on:
$1-\frac{a}{b}$
Al3dium:
So you can visualise it better
is it 1-a / 1-b ?
Al3dium:
Hint: ||common denominator is 3||
1/3
Yes
ah so you just subtract the numerator
Yes
The process is, look for common denominator(a factor that is present in both denominators), which in this case is 3 (bc 1 doesnt matter). And multiply by the common denominator with the fraction that you want to have as common denominator, which in this case we want "1" to be in common denominator. So 1/1, with the new common denominator, 3, 1/3 and multiply it with the numerator 1, so we get 3/3. So its:
$1=\frac{1}{1}=\frac{3}{3}=\frac{3}{3}-\frac{2}{3}=\frac{1}{3}$
@spark lintel
Ah okay
Al3dium:
b-a/b ?
Perfect
Now notice we have
Al3dium:
Now
We'll do division in the second term
Do:
$\frac{2tanx}{1}:\frac{cos²x-sin²x}{cos²x}$
Al3dium:
does the : represent division?
Yes
1/sinx = secx?
Dont bring back sec, we solved it before
1/sinx = secx?
@spark lintel no, secx=1/cosx
cscx=1/sinx
But we dont want that here
Just do the division
2sinx cosx / cos^2x-sin^2x ?
hold on I screwed up one sec
Im not sure
cos^2x + sin^2x / cos ^2x - sin^2x ?
Id love to see from where did you got that sin^2x in the numerator
Its simpler than what you are may thinking
is 2sinx and sin^2x the same thing?
Its cross multiplying
is 2sinx and sin^2x the same thing?
@spark lintel no
Its not the same a^2 than 2a
ya true
is the denominator: 2sinxcosx?
Look, please just do cross multiplying, idk what you did there
Also the denominator you said before was right
Ig ill expand it
Do:
$\frac{2tanx}{1}:\frac{cos²x-sin²x}{cos²x}$
$\frac{2tanx\cdot{cos²x}}{1\cdot({cos²x-sin²x})}$
@spark lintel
Al3dium:
I only crossed multiply
This is the solution
Of the common denominator obv
And we'll remove the 1
$\frac{2tanx\cdot{cos²x}}{cos²x-sin²x}$
Al3dium:
if you cross multiplied how does 2tanx end up in the numerator ?
oh
Ya cross multiplying makes it so much easier to solve now that you've explained it
Al3dium:
Not really no
ok
Hello,
BodhaGuru Learning proudly presents an animated video in English which teaches one of the most useful standard identity - a^2 ā b^2 = (a+b)(a-b) and shows how to use that to simplify algebraic expression. After learning this identity you will learn how to do factorizat...
good ^ ?
he explains it -> (a+b)(a-b) it that fine?
Yes
Oh is it just foiling?
?
yeah
@rich wolf can you take over me?
I gtg sleep lol
The original question is
Sure looks fun
We are trying on RHS
It is
I think i can quickly resume all the steps we did
$\frac{1}{cos²x+sin²x}-\frac{2tanx}{\frac{cos²x-sin²x}{cos²x}}$
Are you allowed to do things to both sides
Al3dium:
@rich wolf idk but its easier, true
Its easier that way
Anyway, my steps were
After original question
Go with double formula ^
Tan x for sinx/cosx
Common denominator in the second fraction below
In the 1-sin²x/cos²x
Which is
$\frac{1}{cos²x+sin²x}-\frac{2tanx}{\frac{cos²x-sin²x}{cos²x}}$
Al3dium:
Now i made the division
And we are here
$\frac{1}{cos²x+sin²x}-\frac{2tanx\cdot{cos²x}}{cos²x-sin²x}$
Al3dium:
Equals what?
Oh, but i took only the RHS
Oh i see
How are you cross multiplying if theres no equality
?
Oh
I call it like that lol
This thing
Idk what to call it to explain him lol
So yeah gl @rich wolf @spark lintel
Thanks for the help
Np
, AMD will do an amazing work as well
@rich wolf are you ready?
trying to make it look like the left side
Exactly we are trying to take the right side and make it look like the left
you only work with one part of the equation not both
Just making sure lol
He left me off with (a-b)(a+b) identity
@rich wolf do you know what the next step is?
No problem
So right now we have $\frac{cosx-sinx}{cosx+sinx}=\frac{1-sin(2x)}{cos(2x)}$
AMD:
So
Wait what happened to the tan fraction?
Oh i just started from the beginning because tbh i dont really get what al3dium was going for
Pretty simple that sec2x-tan2x=(1-sin2x)/cos2x
You're not able to take a call are you?
ok
so if we are proving the right side
we shouldn't be touching the left side what so ever then
I can show you an example
No i mean what does your teacher say about proving trig identities
What do they tell you to do
@rich wolf did you see what I sent
you can only prove from both sides and them make them equal
you are not allowed to do something to both sides
this is just a note I don't know if you did that or not
but just a reminder
@acoustic jungle are you able to hop in a vc room
No because I'm like 2 years old
I can show you what I did though
let me try to find my phone
@Fern#1010
@spark lintel
it's a bit messy because I only had a pen
the x is a multiplication symbol
Fern my bread is going to mold before you come back
I got it thanks guys
@acoustic jungle mold I want to see it mold
@merry abyss is my father
Hello how do you "find the value of the trigonometric ratio."
Show us the question
So tan = opposite / adjacent
Do u know what opposite and adjacent are
@floral elbow
I got it. Thanks for offering to help.
You're welcome
Mhm
I got 35/12 @upper karma
Pls help solve it š¦
@upper karma Man of culture I see, ain't gonna leave anyone hanging
calculate da area of dis shaded region.
where are you stuck?
calculatin da area of dis shaded region.
if you were asked to calculate the area of the whole semicircle, would you be able to do it?
yes
if you were asked to calculate the area of the triangle, would you be able to do it?
maybe
there's no maybe, either you can or you can't
yes
okay
great
so
does it make sense to you that your shaded region is the semicircle but with the triangle cut out
that contradicts how you said that you could calculate the area of the semicircle
consider thales's theorem.
i.e. that is a right triangle
which you would have needed to apply to find the area of the triangle
and if you know 2 sides of a right triangle, what can you use to find the 3rd side?
(which in this case would also be the diameter)
my eyes
why thales theorem ramonov 
inscribed angle works fine i guess.
pain
?
it never ends
I guess I still need help
it's multiple choice btw
I just don't pay attention to math but this is a test and I just wanna get a halfway decent grade
i.e. that is a right triangle
and if you know 2 sides of a right triangle, what can you use to find the 3rd side?
yeah I don't actually remember, usually for simpler problems I literally look at it and compare the length to the known sides and often it actually works out for me
perhaps a famous theorem starting with Py
you found that the diameter is 10
apply certain formula to find the area of the semicircle
A isn't correct
what formula are you applying?
Area of semicircle =
ok and what is r in your figure?
10
no
Aha
oh right
so we never figured out the radius
or I didn't
You didnāt
Son
@upper karma So do you know the radius?
no
What is a diameter of a circle son?
And what is a radius?
Do you see the relationship?
Between them
why are you calling me son
Ok Trey
Now answer my question Trey
Explain to me what a diameter and a radius is
random lines inside shapes that will hardly be found useful to me in the future
Very true but specifically random lines in circles
Now tell me
Do you know what a radius is?
The actual definition
Take your time
Iāll be here all day
š
So you do not know?
half of the diameter
ššš
Son, tell me... did you search that up?
You did not know that before
nope
I randomly remembered it
Oh I see
So just divide that diameter in 2
man I'm out of it
Ok
can't believe it took that long to realize
Alright
@silent plank Aight itās your turn again
so the answer would be C
Ya idk the question just wait for Ramanov
do we... do we help with tests?
yup
@upper karma Ya but whatās the question
see #āhow-to-get-help number 6
yeh its C
kakoolate da urrea of da shaded reejun
yeah
thank u guys for the help
6. Do not ask for help on tests. Any violation of this will lead to appropriate action being taken at mod discretion.
#āhow-to-get-help number 6
it's less never learning it and more forgetting everything cuz I couldn't give less of an f
What about open note quizzes
Can I ask
For those
but this was a solid refresher
kakoolate da urrea of da shaded reejun
i'd say no. don't help on things you aren't comfrotable with
are you purposefully misspelling this
Calculate
I just don't pay attention to math but this is a test and I just wanna get a halfway decent grade
@upper karma
no that's how they actually spelted it
The
Ok
KAWKOOWAYT DAH URREUH UV DUH SCHAYDEED REEJUHN
REEEEEEEE
@upper karma use similar triangles theorem
consider properties of parallel lines
do you know your circle theorems?
alpha and gamma would be equal
how to i find beta on this?
@upper karma inscribed angle theorem
i dont know how to imply that on beta
The angle of a center = measure of the arc
So beta = measure of arc
And the arc you get it by inscribed angle thoerem
i still dont really get it :/
Its simple, notice that gamma and beta have the same arc
yes
because the triangle is rectangular
With the given angle gamma
Use inscribed angle with gamma and the arc
Understood this last step
?
oh
so beta is 66
?
Yup.
ohhhh
yeah that makes perfect sense
Glad to hear
can u use area=0.5b*h on a non-right angled triangle?
my book does it
i thought u have to do area= 0.5 * b * h * sin(a)
area = 1/2 bh where h is the altitude relative to the base
even if there is no right angle in the triangle?
doesn't have to be a right angle
area= 0.5 * b * h * sin(a)
not a great choice of variables
yeah lol i see why
= 1/2 ab sin(C)
indicates that you're using two sides and the angle between them
yup
move all terms to the LHS
Yeah i already did that
now common denominator
How do I find the perimeter for this shape?
i have the length from the middle to a point
and the radius of the circles taken away
what is the length from the middle to a point
@rich wolf Im still pretty confused on what im supposed to do
show us what you are given
@upper karma find the circumference of each semicircle
There are 6 semicircles
=3 circles
They don't look like semi-circles
They look like 6 inverted portions of a circle
If we turn them to the other side, they form a complete circle
I'm not sure about that, but I'm pretty sure each portion is not a semi-circle
tangent theorems, angle around a point and angle sum of a quad will allow you to find the degree of each arc
@upper karma length from middle to point is 5
bring everything to the left side
and...
express tan in terms of sin and cos
multiply both sides of the equation by something to get rid of the fraction
apply a Pythagorean trig identity
^
https://i.gyazo.com/thumb/1200/233a96032271ec65843a35e696316d1b-png.jpg how do i do this?
ik the simplified equation is
-16t^2+62x-52=0
but idk where to go from there
Seems hot
what does that mean
You can use the quadratic formula or complete the square
or use product sum factor
That looks very difficult to product sum
oh he has -52 as his c value
i was using 4
cuz thats whats in the question
yah use the quadratic formula
Do you know how to use the quadratic formula, or how to complete the square, sam?
@spare plaza
Yup i just finished it :D
Hey, can someone help me real quick with a refresher geometry problem? I completely forgot how to do this lol
you could estimate it without trig, but i dont see a way to do it exactly without using trig...
huh
is this from a geo class?
yeah
I used to be able to do it like heckin good. but now i cant bc its been so long lmao
im in 10th grade
Use a sum or difference formula to write a formula for cos^2x. Express the result in terms of sinx and cos2x.
<@&286206848099549185>
please
help
cos72
you sure you aren't meant to use any trig?
What is the emote reaction
what is this
Idk
thanks gang
Iāve seen a bot like this before
twas correct
It auto reacts
Yes?
i was so confused, I have never seen like any of this stuff b4 lmao
thanks man
someone help
please
Use a sum or difference formula to write a formula for cos^2x. Express the result in terms of sinx and cos2x
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
@here
what have you tried
i have no clue how to approach thjis
because
making cos^2x=-sin^2x+1 wont do anything
Well you are given the hint of using a sum or difference formula
and expanding it to cosxcosx
wont do anything
yeah
thats great
but im gonna have to make cos^2x to become something
before I use those formulas
Im gonna need two angles to be added
or subtracted
I was thinking of doing
cos(x+0)cos(x-0)
and that does
absolutely nothing
you said that you can write your answer in terms of sinx and cos(2x)
can you expand cos(2x)?
I was thinking
of doing a double angle formula?
you can expand cos2x = 2cos^x-1
or -2sin^2x+1
yes, that's the same thing as sum formula of cos(x+x)
from cos(x+x) = cos(x)cos(x) - sin(x)sin(x) = cos^2(x) - sin^2(x)
yeah
i realize
but I simplified it by substituing one of the pythagoroas identities
so I got
2cos^2x-1
can u just tell me the answer
i got 5 more min
before the hw closes
and i cant turn it in
well if you rearrange that, you get cos^2(x) = sin^2(x) + cos(2x)
yeah
which should work, if not, you can use pythagorean on sin^2(x) (by adding cos^2(x) to both sides)
then you'll get the normal power-reducing formula for cos^2(x)
that is 2cos^2(x) = sin^2(x) + cos^2(x) + cos(2x) = 1 + cos(2x), so that cos^2(x) = (1+ cos(2x)) / 2
ty
you might consider multiplying the left-hand side by cos(t)/cos(t)
and perhaps also doing the same to the right-hand side
but
I thought you had to only focus on one side
and find the proof from there?
so confusing./
maybe you mean, move on
from the left side
and try right
omfg
I got 0
I thought you had to only focus on one side
there is nothing wrong with doing some simplification to the left-hand side, then independently of that doing some simplification to the right-hand side, and then proving that the simplified versions are equal
ann
what
hi
hi
tiring
If tanA = 5/12 with A in Q3 find sec2A
I don't get it
sec2A = 1/2sinAcosA
actually
1/1-2sin^2(5/13)
you're missing some parentheses here
How can an expression transform into an equation
Akward you have an "=0" missing in the 1st pic you sent
@granite elk
So, do common denominator
From what you got, do common denominator
i simplified what i got
What? Can you follow my instructions
?
Do common denominator on the full expression
You should get up to $\frac{1-\cos²{x}}{\cos{x}}-(\frac{3\cos²{x}-2\cos{2}}{\cos{x}})$
@granite elk
Lmao
rip
Mmm
You should get up to $\frac{1-\cos²{x}}{\cos{x}}-(\frac{3\cos²{x}-2\cos{x}}{\cos{x}})$
also the frog pfp really suits the the reply hahahaa
Lol
akward u havea great name and pfp
lol thx
Al3dium:
Now
Follow this? @granite elk i only did common denominator which was what i told you to do for 5 mins
ok
Understood this step?
yeah
is that minus meant to be there
next to the brackets
because its going to affect the - inthe 2 cos
Substracting
$1-\cos²{x}-3\cos²{x}+2\cos{x}$
Al3dium:
is that minus meant to be there
@granite elk yes it is
ok
Al3dium:
Al3dium:
Np 
SA = hp + b?
SA?
surface area
No its $A_{total}=(\frac{b*h}{2})*6 + A_{base}}$
what does the a represent
Al3dium:
Compile Error! Click the
reaction for details. (You may edit your message)
Now lol
ok that makes more sense kinda
Ok now
what would atotal represent
Okok np
Gonna ask this here again, how to find the perimeter? Didn't quite get the answer I was looking for last time.
I have the length from the middle to the point (5cm) and the length of the radius of the circles that are taken away from the sides (also 5cm)
I need to find the perimeter, but I don't know how.
visually, its scuffed
cause if the circles werent taken away then the original circle would be the same size as the circles taken away
@upper karma assuming that shape is a hexagon, the perimter is just the circumference of the circle
if you construct another circle connecting the the radius of the star, it'll be a rhombus
with 60 degrees
and there are 6 of them
I NEED HELP PLSSSSs
@brisk ginkgo just post it bruh
@brisk ginkgo "help, help, I need help", 5 minutes later he's offline
Lmao
what I understand from that is that the test is over and he's no longer interested in getting help
Prob ^
Which is pretty sad and dissapointing
HELP HELP HRLP PLS
haven't you learned to figure this out in class or something
