#geometry-and-trigonometry
1 messages · Page 284 of 1
So, for number 3, here's a hint
cosx sinx at the top
Divide numerator and denominator by $\cos^2(x)$
Abhijeet Vats:
Oh you just copied those steps out from somewhere else, then?
no?
i just got stuck
i dont get how to divide by cos^2x
like how do you do bothn num and denomm
$\frac{\sin(x)\cos(x)}{\cos^2(x)-\sin^2(x)} = \frac{\cos^2(x)(\tan(x))}{\cos^2(x)(1-\tan^2(x))}$
Abhijeet Vats:
Make sure you see why the above is true
huh
@vague berry aight srry i was helping on another channel and forgot about you
Whats the matter
i just used the fact that:
$$\cos^2(x)\tan(x) = \sin(x)\cos(x)$$
Abhijeet Vats:
Like I said, try to look at that and see why it must be true
yea
so you can finish it off from there
for 3, I'll give you a hint
$\cos^2(x) = 1-\sin^2(x) = (1-\sin(x))(1+\sin(x))$
Abhijeet Vats:
Is the exact area of a circle found by leaving answer in terms of pi?
Yeap
👍
hey guys just a very quick question please
the principal is just the angle so like 340 and the acute angles will be 20
is that what principal angles means..?
@foggy beacon is it a test
Lol
but what does principal angle mean
Some ppl sadly have
Wait a sec
Find Principal Angle and Acute Angle from the given conditions.
This'll do
principal angle is the coterminal angle between 0deg & 360deg
do you know what coterminal means?
they have the same ratio so I think it depends on the Quadrant
I thought that getting it was like the same way as the acute angle
but plz help me
do you know what coterminal means?
i think getting it is the same way as the acute
it has the same ratio
as the angel
wdym ratio
like if we take the sin of that angle its the same as the sin of the coterminal
@weak shoal
by that definition, 0 & pi are coterminal. and that's wrong @foggy beacon
,rotate
Abhijeet Vats:
just factorize $\cos^2(x)$ from the denominator
Abhijeet Vats:
$\cos^2(x)\tan^2(x) = \sin^2(x)$
Abhijeet Vats:
oh its the same thign ?
dude, you gotta think lmao
just think through it
oh its the same thign ?
@vague berry an equation by definition can be switched or moved and will keep being true
oh
$\cos^2(x)-\sin^2(x) = \cos^2(x)-\cos^2(x)\tan^2(x)$
Abhijeet Vats:
Please engage your brain and think.
i didnt see that
No you are not lol
You're welcome.
Then for question 3
$\cos^2(x) = 1-\sin^2(x) = (1-\sin(x))(1+\sin(x))$
i can do that in my head
Abhijeet Vats:
aight, good then
use parentheses please
sorry
and no, that implication does not immediately follow
there's an intermediate step that you're forgetting
but the idea is essentially correct
It wasn't an issue. You're welcome.
someone help here, https://i.imgur.com/TDuE8gh.png how would you know if the point of intersection is a right angle
measure the angle using a protractor 
lmao
well i do draw it, but it's hard to get accurate angles without a protractor
Then post it and ill confirm if its sine's law
No lol doesnt need to be accurate
Just a sketch
Vats was joking
ok im sketching
thats the best i can do
lol
forgot to label b
Wait I think I just figured it out
Convert the angles to decimals so it's easier to work with
330 27' is around 29.55 away from the start
Wait I think I just figured it out
@pine oar did you
uh idk where you get 29.55
360-(330+27/60)
part in parenthesis is the conversion from degrees and minutes to decimal
do you mean $360-(330+\frac{27}{60})$
Al𝟛dium:
or the 60 is all the way
yes that
,calc 360-((330+27)/60)
Result:
354.05
Result:
690.45
,calc 360-(330+27/60)
Result:
29.55
What is the area formula of a cone that has semi circle basically an ice cream?
@upper karma is the way I figured it out wrong or is that okay
@pine oar drawing was right
Does the word "bearing" change anything
Im not native so idk what that is
malix the drawing may be right but it doesn't look right lol, how am i supposed to put a right angle onn that
If a bearing is given strictly as an angle it is measured clockwise from north
Oh so it does change lmao
Yeah
Ok my drawing is voided
And there’s also bearings given as (N or S) angle (E or W)
N 30 degrees E means 30 degrees east of north
It’s where you put the angle
As "bearing" isnt familiar for me, id trust malix
@pine oar you already have 2 right angles up there you can use
And a coincidental and convenient third you will have to realize by calculation
If i have a right triangle, are the other two angles 45 degrees?
and then subtract that from 90
Gets one internal angle on the right
ok perfect
If i have a right triangle, are the other two angles 45 degrees?
@lucid orbit not at all
i get it
oof
Only if both (non hypotenuse) sides are the same length will both other angles be 45 degrees
Well its basically doing sine definition twice lol @pine oar
wat do u mean sine definition?
$\sin(x)=\frac{\text{opposite side}}{\text{hypothenuse}}$
Al𝟛dium:
can you do that without a right triangle?
well we have no values for either side of the right triangle
h is a side for both triangles
ok
And x forms part as well
Of both eq
@pine oar have you got it or may i write it
i was gonna say the other known side of both triangles are functions of x you can easily determine
Aight wait a sec
aite
base of one triangle (with larger angle) is x
base of other triangle (with smaller angle) is x+155
$\begin{cases} \tan(11"30')=\frac{h}{x+155} \
\tan(38"40')=\frac{h}{x} \end{cases}$
Al𝟛dium:
" is °
@pine oar
Im srry it was tan not sine
Its kinda late for me lol
Need sleep
,ti
The current time for Al𝟛dium is 01:52 AM (CEST) on Fri, 22/05/2020.
hmm
Can someone help me telling me if it’s good? I have to calculate the dimensions of a rectangule if the perimeter has a length of 44cm and his area is 105cm2
@upper karma ok i worked it out
ty
sorry for late response
was writing down all the info
Np
isn't -53 already an acute angle
how can i find the acute angle of -53 can someone please guide me
I'm not sure about the terminology, but I think the principal angle is the angle from 0 to 360 degrees that coincides with your angle.
And the related acute angle is the angle you form with the x-axis.
As in, if you had -30 degrees, you can see it forms an angle of 30 degrees, ignoring the sign, so the related acute angle of -30 degrees is 30 degrees.
Not sure how to phrase that.
hi! im almost done with school but i have two assignments left that i cant figure out at all. One is over finding the arc or central angle. The other is Inscribed angles and sector area. This is geometry stuff, if anyone is able to help id love for you to dm me! im desperate
er you can ask for global help in the channels a,b,c, ...
@loud glade just use the fact that a circle is 360 degrees and a diameter splits the circle into 180 degrees
Watch some videos online
Inscribed angles and area of circle or sector
@loud glade Have you tried them yourself first atleast?
yeah a few times
ive even looked at her reviews
i think i understand the super simple ones like number 3 on the second page
but everything else is difficult
what strategies do you reccomend I do to organize my time bc I want to take geomtry over the summer as an online class. They expect you to do 7-8 hours of work alone with 90min online classes and and 3 exams that are proctured virtually. Any resources, textbooks, youtuber you reccomend since im a slow learner and we have a month and a half to learn everything with a quiz every week
bc this is stress full since its from june 22nd to june 30th
th up side its only pass or fail
MindYourDecisions
wat?@upper karma
Its an awesome yt channel dedicated to geometry
oh sorry I mistunderstood, thanks for the reccomendation
help #help-2 👉 👈 😳
hey guys can someone please please guide me through this one question
here's the equation
idk what to do next
its 2
can someone please tell me what I should do after this step
ok
in the interval [0,360°] which angles give sin(y) =1/2?
hint: there's two of them
yes but like i dont know what to do in the bracket
do i just like plut it in the calulator or what
yes
that will give you two possible solutions for x then
just plug in and solve
for example,
one solution is y=30°=x/2-90
so x/2=120
x=240
get it?
so find the other solution, and you're done
oh shit wait
x is in [0,360] not y
bro i swear you're too smart
if x is in [0,360°] then y is in [-90,90]
so then, only 30° is needed
150° is outside the range they're asking
sorry for the confusion
so only one solution
okay thank u lots lots bro ❤️
What are dependent events in probability?
@upper karma events that depend on the other for example, if A occurs it will change the result of B but if A doesn't occurr it won't change B. Numerically, gotta prove that $P(A)*P(B) \neq P(A \cap B)$
Al𝟛dium:
There are more twins to this, let me know if you need more
Ok ty
Also this isn't the channel to ask about probability but oh well
Np
for what
send me screenshot of 1 problem
@tame ore ay deal
I’ll doo all of it
paypal
wdym
u want more?
👁️ 👄 👁️
Do u
Nah esmerelda, keep your money
I’ll help
@tame ore Aight fuck it, I’ll do it for free
@tame ore lets go dms
Bruh
Hf
Bitch
😆
You see how it resembles a right triangle
i guess
but i dont wanna solve it 
@upper karma see what I’m talking about
He wants someone to do all his work
And I’m the man for that
aye
@tame ore lets go dms plz
I thought that was against the rules or smth
😔
It is
But I’m
A
Idk the word
Haha you’re fine
@royal dew Wait is this against the rules?
@copper valve
no free lunch
Is it true that those triangles are similar to each other? There is a bisector.
angle bisector
Ok, so there must be some additional information.
Yup
You should look up the triangle similarity theorems
Like AA, for example, where two angles have to be congruent
What can we say about areas of those triangles? Are they the same?
what
We can’t assume anything about the area of those triangles, niko ^
What we know about those triangles: they each have an angle and a side that have the same measurements.
hey guys, I was wondering if in this problem i had to subtract the area of the base of the cone from this when solving for total surface area of this shape. Do you have to remove the base of the cones surface area in order to solve?
for surface area of the total problem
Question asks me to
Eliminate the parameter to find a Cartesian equation of the curve. of x=sin^2theta, y=cos2theta, -pi/2<=theta<=pi/2
By adding the equations I get x + y = cos^2theta
Not sure where to go from there, any advice?
$\begin{cases}
x=sin^2{\theta}
y=cos2\theta
\end{cases}$
Agent:
θ = arcsin(√x)
y = 2cosθsinθ
y = 2cos(arcsin(√x))sin(arcsin(√x))
y = 2 √[1 - x] √x
What is the length of the radius of the radius of a circle whose area is 100pie
Oof, please see the rules on helper pings
Wait 15 mins before pinging
k sorry i deleted it
The radius of a circle with 100π area:
A = πr²
A/π = r²
√(A/π) = r
See how that rearrangement works?
Hey Kaynex was the previous response for me? Not sure how cos2theta goes to 2cosθsinθ
Oh shoot haha
I got that confused with sin(2θ) mb
Use cos² - sin² instead
Actually, use 1 - 2sin²θ
yea thats what i did, and tried combining them and was left with x + y = cos^2θ
either way you are left with cos^2θ
See what I did
@boreal narwhal Do you know the properties of a parallelogram?
I believe so, Why?
Then apply your knowledge in solving them
What do you know about the sides of a parallelogram
?
Yes
Just set them equal
And solve for x/y
Opposite sides in a parallelogram are equal
When I try to set them equal I get a fraction
Ya so what
so would the answer be a decimal/fraction?
Depends if your teacher wants it a specific way
Otherwise anyway is fine
Fractions are good tho
Since decimal formation can be enormously long
@boreal narwhal Do you understand the 2nd problem?
Yeah, i got 39/2 for A
no not yet
Have you not learned anything about the angles in parralelogram?
Well, opposite angles in a parallelogram are equal.
And consecutive angles are supplementary.
@boreal narwhal Do you understand?
so would I set it equal to each other or180?
Explain more
What would you do
@boreal narwhal
Didn’t quite understand what you are implying
Sorry
do I do 2b+41 = 180
No it’s adding the 2 angles together
Another tip is that all angles in a parallelogram added up = 360
If you had that angle = to 180 then it wouldn’t work
@boreal narwhal Do you want a video explaining this?
sure
Hold on
Theres this one https://youtu.be/Kj1p8j-aoN0
Art of Problem Solving's Richard Rusczyk explores the angles of a parallelogram.
Love math? Learn more: http://bit.ly/ArtofProblemSolving
Which specifically explains the angles
And this one
This geometry video tutorial provides a basic introduction into parallelograms. It explains the properties of parallelograms and how to use it calculate the missing sides and missing angles of parallelograms. It contains plenty of examples and practice problems for you to wo...
Goes more in depth about all the properties of a parallelogram
@boreal narwhal Good luck!
Thanks
A little
so angles a and angle of 36 deg are opposite angles, yeah?
is the same true for angles b and 113 deg?
no
i cannot draw it now, but try to draw two parallel lines by youself
and any line crossing them both
and look at properties of inner angles
Wait but angle b and 36 are identicle
why?
we don't care how do they look
maybe painter was drunk, huh
what we care is numbers and properties
look, move upper base of trapezoid down that way it overlaps lower base
what can you see?
i mean angles a and 36 will yield some property
opposite sides are equal
Use system of equations after that
so u'll get two linear equations
Would it be 7x+6=12y+7?
Move all the variables to the same side of equation and then use system of equations
Make 2 separate equations
wym?
7y+7-5x=0
2x+6-5y =0
Why do you subtract 5x?
Why do you subtract 5x?
opposite sides are equal
Because 7y+7=5x
if you subtract equal from equal...
And then I moved all variables to one side
So how would you solve 7y+7=5x?
You also have the other pair of sides
by the help of second equation
5y=2x+6?
Not really
Substitution?
How would I do it
How would I do it
@boreal narwhal express x in terms of one of the eqs
and substitute it into the second
can someone help me pls
I know this is geometry sort of which is why I dont know what im missing
do you know sines etc
i used sin to find 1 other side
yes
sin 30 is 1.5/3
so the opposite to sin is 1.5
and I tried to find sin of 60 because we know its a 30 60 90 triangle
just use pythagor theorem then lol
it give s me the same result
it just gives me a decimal
and I dont know how to accurately calculate perimeter and area
um wtf is that...
im confused
I did
Then what’s the problem
I know one side is 1.5 and the other is a decimal
you should know the exact ratios for special angles
and not be entering this stuff into a calculator
sin60=sqrt(3)/2 sin30=1/2
exact trig ratios for special angles
oh we r doing that triangle??
wtf why am i so dumb
So do u get it now?
yea 3m=2a so a is 1.5
Yes
That’s not a radian
radical
It’s 1.5 root 3
use sqrt() for square root
if c is the variable you are using to denote your base then yes
but it wants me to find the exact perimeter and area of the triangle
and when I add everything it gives me a decimal
how do I know when to stop
don't evaluate the square root
leave it as is
and not be entering this stuff into a calculator
I dont know how to solve it normally if I dont use a calculator
your sides are: 3m, 1.5m and 1.5sqrt(3)m right?
add/combine the terms you can
you can combine the 1.5m and 3m
and your exact perimeter would just be:
(4.5 + 1.5sqrt(3)) m
Oh I didnt know they wanted me to leave it in that form
so for area its the same just (4.5 x 1.5sqrt(3)) m
?
area is half of product of cathetes
what is cathetes
not knowing what cathetes is and using area is half the product cant I just make it (4.5 x 1.5sqrt(3))/2 m^2
fancy term for legs of a right triangle
A = 1/2 bh (where h is the altitude relative to b)
ahh
or generally, A = 1/2bc times sine of an angle between sides b and c
that can be simplified further
idk this site is very simple and maybe wont recognize it
@azure reef the sides of a right triangle adjacent to the right angle are called legs in english.
how would I use fractions here?
@dark sparrow and cathetes in Greek
1.5 = 3/2
oh
continue to simplify: \
$= \frac12 \times \frac{3\sqrt{3}}{2} \times \frac32$
ramonov:
$\frac{9\sqrt{3}}{8}$
Commander Vimes:
also wasn't directed at you
ohh
I really need to practice math again im a disgrace
so this would be the final answer right?
yep
thanks
I have tetrahedron with sides all equal to 6. There is a sphere inscribed in that tetrahedron. What is height from base of the figure to the mid of this sphere.
No idea
quick question --> might be dumb, but it's 3:00 AM so here goes:
is it valid to say that if all of the angles in a polygon are equal, so are all of the sides?
Or just any non-square rectangle
Can anyone explain?
_
ramonov:
"0/0" does not mean "limit does not exist"
So it's 1?
ramonov just told you this particular limit is 1, yes
what's "it"
sin (x)/x = 1
It approaches 1 but is written =1 ?
the limit is equal to 1. when a limit is equal to a value, that means it approaches that value
no, ramonov did not write $\frac{\sin(x)}{x} = 1$
Ann:
he wrote $\lim_{x \to 0} \frac{\sin(x)}{x} = 1$
Ann:
Wait I hv to process this
...
-> 0
To compensate for the 0?
you're overthinking it
like do you really not understand why $\lim_{x \to c} (x+5) = c+5$ for example
Ann:
x-c=0
...
That's how I've always looked at it 

2x - π/3 -> π/3 - π/3
How?
2x approaches pi/3
what do you think 2x - (constant) would approach, if not pi/3 minus that same constant
0
sigh
idk what the hell you mean by "compensate for the 0"
pi/3 - pi/3 = 0
Guys why does this work I cant get it
yes but i dont get how to get the cos^2 there
And then the vertical part of the triangle is sin
Pretty sure its something with geometric mean
that smaller triangle is also a right triangle
cos(theta) = a/cos(theta)
a= cos^2(theta)
(where a is the length of the indicated segment in question)
Ok so i still dont get it here is a picture
@sick isle Nice bucket
thanks man its my home
ok so what's bugging you
I cant figure out why that length is cos²x
Where x in the angle from x axis to line drawn
i mean Ramonov explained it
You apply cos x in that little triangle
cos(x) = cos^2(x) / cos(x) <=> cos^2(x) = cos^2(x) and it checks out
Yo
Yo
Yo
@yoyoyoyo
help
how do I find a surface area of a triangular prism with height and a base?
@upper karma base times height
Oh wait
Nah that’s area
yea was aboutta say
It’s
You just calculate the area of all the sides
And add them all together
http://www.freemathvideos.com In this video series you will learn step by step how to solve different geometry problems based on my teaching of Geometry in highschool. We will cover topics throughout the whole curriculum. Use these videos to help you with your homework and s...
ohh okay
You just calculate the area of all the sides
And add them all together
ngl i find it kinda weird that people seem to not know or not remember this simple idea
@dark sparrow yes
Lmao
same
I came here for math help not to be insulted by smart asses
this wasn't intended as a jab at you specifically
It was implied

I don't think it's their fault specifically.
If someone is confused about something like that, it's more likely that their teachers failed to explain to them what surface area actually IS, which is a bit sad : /
reminds me of a sad story that my professor told me
he said his friend was teaching at a middle school, and the principal was spectating the class one day
one of the students asked where the surface area of a cylinder formula comes from, and she gave the intuitive and memorable explanation
then afterwards, the principal told her "that's not part of the curriculum, you can't teach that"

wat
there are 6 questions here
which one do you need help with
if multiple, which one do you want to start with
@royal otter
alright, so what is giving you trouble for #2?
That sin alpha is that stuf there and i would say everything can u do at least the 2nd question
I have a test so id ont have time for explaining
this IS against the rules
I just joined
this IS against the rules.
Okay
<@&268886789983436800> get their ass
I wont ask for help then
Thanks anyway
But still good server for getting help thi
;-;
Pls dont
Hey hey be undearstanding a bit
Nah @royal otter, screw that. You are cheating over your classmates who did honest, fair work up to this test : (
Oh wait, shoot why did I ping you you are in a test
their butt has got got
thamk u
this is against the rules of not only this server
google found me chegg servers
Chegg study :O
😮
😳
idk if this is the right place to ask how to calculate the surface normal on a sphere 😳
It’s almost like the 10 min time to read the rules is ignored...
wot
I have this problem where "cos b = -(9/13)" and b is an angle greater than 90deg but less than 180
Using arcos b I got that angle b = 133deg
But I am so lost as to how to get the rest of the trig functions now, was wondering if someone knew what steps to take now
oh yeah i used (-9/13)
use pythagorean identities to help find the other trig ratios
Although I'm not sure if I should have or not, since the text is this:
use pythagorean identities to help find the other trig ratios
@silent plank ah okok will do
thnx
A line segment has one end point A at (-3, 5) and a slope of -2/3. State Two locations (x, y) of the other endpoint B.
Okay so what do you propose might be a good way of attacking the problem?
BRUH, dont multipost. @vale herald
? He posted in linear algebra and I told him to come here
What do you mean you answered me?
you may wanna check #prealg-and-algebra again maybe
u can't use point slope formula to graph it..
who told you it was used to graph 
Also, you could use point slope form to generate a graph...though that won’t necessarily help with your specific question
yes
I just don't know the rules that well...
I'm looking at an example in my book
yeah you could
but it doesn't look like this
ty
I'm having trouble feeling like it's "correct" since I have no way to "Verify" it
https://complete-concrete-concise.com/mathematics/proving-alternate-interior-angles-are-congruent-the-same/ Proving Alternate Interior Angles are congruent
Yes derive theorems and equations to fully understand things
^^^
I try to derive it before looking at it in the book
Kinda fun actually
👍 👏
🧕🏼🤲
Hello, can anyone help me on my quiziz hw?
So if i have am apothem on a hexagon of 11
What is area
So is it 22 times 22?
@upper karma
Apothem?
a line from the centre of a regular polygon at right angles to any of its sides (dictionary).
no
Why?
Circumference is 20pi
R times 2
If its 8
no
Then its 16
I think yo ucan solve it from tehre
So
Yeah
Yeah
Thats why d was correct
Haha
recall the formula for the area of a parallelogram
Why do you post them here if you know how to do them
Idk, when i post it here and you guide me, i somehow know what to do.
It like comes to me
Not awesome
Oh
Yes
well imagine a line from the top two points of the trapezium to the bottom line
Ok
Im just going to assume its a trapezium
Yes height
Yes
Whats trapezium?
I think you can handle it from there
Whats trapezium?
I have a question regarding the graphing of reciprocal functions, where should I go?
@supple sundial Perpendicular
@lavish glacier Forget the trapezium
Ok
Yessir
perpendicular?
No
@supple sundial Answer my question
@supple sundial Perpendicular slope
Do you get it or not
ok thank u for telling me
Ya I don’t get it either
What trig function do i use?
@little osprey How does one use a system of equations to manually find the graph of a function in the form y=a/x-h+k
90 60 30 triangle
@supple sundial Could you just go to one of the #❓how-to-get-help channel
Use exact trig ratios Var
You can also just simply use the 90, 60, 30 triangle rule
The height
Because the area of a trapezoid consists of finding the height
It doesnt say its a trapezoid
So but i dpmt have any other variables
xi
Ok
whats tan 60