#geometry-and-trigonometry
1 messages · Page 258 of 1
Then you can use double angle
Buddy I know the formulas
sass
That's not the part I can't get past
Ok lol no need to get cranky
Sorry just felt like it was getting repetitive
I can show you the progress I've made so far
I tried getting to the question from what we had to prove
Cos^2(theta)+cos(alpha)=0
That's what that led to
I mean that's what I need to prove
Or that Alpha=2n*pi
This is what I got after trying to convert it into a quadratic and do some stuff
If you know any relevant formulas to this then it'd help
if you convert it to quadratic there shouldnt be sines and cosines
pulse use the law of sines
Not good at that
sin(A)/a = sin(B)/b
oh
you just use the sum of triangle = 180 and right triangle = 90 and 28 degrees is 28
I have it in #combinatorial-structures
This channel is taken @acoustic jungle
Oh shoot that message is late
Sorry for that
no worries
same stuff pulse
Hey max,think of anything?
I'm stuck and can't even derail myself to think of something else
Alright take your time
but i dont see how they got further
Same
Is A 60
Ye
So what do you do
he only has to find the angle
Oh okay
Use Pythagorean theorem to find y
And then you can find the angles of that smaller triangle
Also if you are struggling with basic trigonometry you might want to brush up your theory
It would save a lot of time
Hmm
I could tell you but that would destroy the whole purpose
Of learning lmao
Alright so id suggest watching a few videos from khan academy
maybe just give him the formula?
😐 khan academy
all of them involve pythag?
He's doing basic trigonometry,so I reckon yeah
Oh ok
we can give him the formula and let him work out the answer by himsef
freaks
im confused
if you multiply both sides by sin(theta) and sin(theta-alpha)sin(theta+alpha)
you get that sin(theta) = 2sin(theta-alpha)sin(theta+alpha)
Yeah
and under the assumption that alpha = 2npi
sin(theta) = 2sin(theta)sin(theta)
and i just realized that i added instead of multiplied
i was gonna say sin(theta) = 4sin(theta)
but math doesn't work like that
I don't get your doubt
And also
If the alpha=2n(pi) condition doesn't hold the second one will
no but it has to hold
cause its the end of the proof, but its not 4sin(theta)
its sin(theta) = 2sin^2(theta)
1 = 2sin(theta)
Share the proof
1-2sin(theta) = 0
We skipped over a bit of stuff I think
No worries
i might come back to it
law of cosines
Idk what that is
Yeah or if you don't want to use trigonometry you can draw a perpendicular
It will give a positive X and a negative one
Lengths aren't negative
Lmao nvm that's way too lengthy
Use loc
@onyx cloud that question is wrong
which question
The one i asked
what was wrong about it
the textbook one?
@onyx cloudcosec(theta + alpha) + cosec(theta - alpha) = 2 cosec(theta)
This is what the question should have been
ah i see
It was stupid of me to not consider the possibility of the problem being wrong
I've been trying to do it for so long
If the image of point J under a 180° rotation about the origin is (7,-3), what are the coordinates of point J?——- am I post to apply the rotation to the coordinate point (7,-3)
I’m confused cause it doesn’t give me a picture for reference
image and preimage are geometric terms
Oh I’m just finding the pre image
that's a tangent line 
...
that is not the diameter unless you are given more information
wait this is solvable??
You can't solve this without knowing angle DAB
if you visualize this, the height can be anything without any restrictions
wtf
Yea wtf this has infinite solutions essentially
DAB is a right angle I think, if you look very closely
there a small right angle symbol
Ahhh yes that'll do it
Ok so the strategy is to do a bunch of systems of equations using Pythagorean theorem
Label the unknown sides with variable names for easiness of writing
And then you get 3 unknowns with 3 equations
how do i figure out the changes to a parent function from the equation
i just completely forgot everything from functions from last year
do you have a specific question in mind
test and quizzes are elements inside a subset of assignments
therefore if assigmnets and allowed, so are tests and quizzes
checkmate
🤔
sorry i watched a video on introduction to set theory and i thought i was cool
So i can’t post it?
yeah go ahead
ok so lets work through the first one
problem a that is
are there any functions you can't recognize?
the last two
i honestly didnt notice that
the more you know 😄
well either way
now that you know all the parent functions we can work on part b
so looking at the first one
what is the parent function
a quadratic so f(x)=x^2
i dont remember entirely
yeah i gotchu
its a good start
so what domain is
is the possible values of x to satisfy the function
so if our function is say
f(x) = 1/x
then x can be all real numbers
except for a single number
that number being 0, as 1/0 is undefined
so if we apply the same logic to x^2, what is the domain
yep
thats right
now
that's for f(x)
what about for 2f(0.5(x-1))+3
(i got that function from the first picture btw)
im not sure
so lets do it looking at the graph
are there any x values for the red curve that don't work?
um im not sure what you mean but you're right
its no
therefore the domain of f(x) is x is an element of all real numbers
or
x ∈ R
Sry
since x can be any number
@silent sequoia
thats right
but what we say is that x can be all real numbers
not that it matters too much rn but yeah
now you wanna do range?
range cant be below 3
what can't be below 3
the y
how do you write that mathematically
y is greater than or equal to 3
yea
pretty much
like actually i think its 100% what it means
but ok you're good with range and domain
now intervals of increase and decrease
do you know what that means
horizontal phase shift and vertical
oh
no
ok
so interval of increase
this is asking for what values of x
the y is going up
so lets work it out with f(x) = x^2
looking at the green graph, for what values of x does the y increase
thats where the centre of the red line is
0
so is the y increasing at 0?
so i notice what you're thinkning
but what about .01
or .0001
or .0002
or 1
or 10
is it a single value of x or is it multiple values of x?
single
i mean
multple
because its increasing the same from other side
aswell
Max can I ask my question when u guys done
increasing means the y goes up
as the x goes up
pulse head over to one of the #❓how-to-get-help channels
decreasing means the y goes down
as the x goes up
did i lose you
No
ok
so looking at the graph one more time
where in the graph does the y go up as the x goes right
1
1 what
It’s going up at any point on the right isn’t it
On left
I’m not sure
so what does -x mean
X is above 0
X is greater than 0
perfect
so increasing for x^2 is x>0
and decreasing is x<0
what about the red function?
wdym?
Where the line turns
from doing what to what
Not sure
ok well you're right
its turning from decreasing to increasing
or increasing to decreasing
so for the green function where is that at
There is none
but the function increases for some x
and decreases for some other
so it has to turn at some point right?
1
yep
so now
can you try the other ones
and see how you do?
i'll be here if you need hel
p
K
pulse do you know pythagoras theorem
Ok
can you give me 2 secs while i draw something
so this is pretty much what we have right?
Yeah
so theres a few things we know
Theirs 3 triangles?
yep
so i labeled the sides to make this clearer
now
do you know what the hypotenuse of a right triangle is
I heard of hypotenuse
on the first image yes
Yeah
but focus on this second one for now
what pythagoras theorem tells us
is that the hypotenuse
(we'll call it c)
has a length that if we square (c^2) will be equal to the sum of the other two side lengths squared
we'll call them a and b
so this looks like:
a^2 + b^2 = c^2
Ohhh I’ve seen this
A square plus B square equals C square
Ok
this one has the labeled sides sorry
theres 3 different hypotenuses
can you tell me which ones?
A^2+C^2=B^2
i don't see how you got there
but focus on the hypotenuses first
here i
i'll highlight one
the hypotenuse is in red
and the legs are in yellow
thats 1 of them
there are 2 more in the image
can you name them
yes
X?
no
Line CB?
yep
so now we know that y, z, and cb are hypotenuses
and let's call cb a for simplicity
so a, y, and z are the hypotenuses
we good thus far?
Yeah
alright
now what do we know about the side lengths of these sides based on pythagoras theorem?
let me make the question a bit simpler
That they are the same
they aren't the same length
Value? I
nono
Ok
Maximo:
do you see how i got here?
😐no
so z was one of the hypotenuses right?
Yea
The length?
do you remember pythagoras theorem?
A square plus B square equals C square
and what is c in that equation
20
The longest length
which is the hypotenuse yeah
so
if we take the triangle again
can you use pythagoras theorem for the triangle i highlited?
Yes
how would that end up looking?
A+B=Z
You can also use similar triangles
so pyhtagoras theorem is $a^2+b^2=c^2$
Maximo:
I dunno
wanna give it a shot
Fishraider:
yes
oh
well you can also do a more tedious way
write out 3 equations with pathetic theorem
I would just make these 3 equations add up to 360 and then solve right?
right
ok ty
did you get the three equations
No
use the pathageorean theorem and get them then
do you see the three right triangles
Yeah
it should be
Ok
help>?
should be theorem for that
I think I got it
oh yea
but like my teahcer cant teach
so i have no idea how to apply the theorem
all you need to know is isoceles triangle
and from the end of the circle to a chord is have the angle to chord subtends
I actually like this problem a bit because it requires some steps
also whenever you are given a problem use every piece of information, have you used the 50 degree info
@ancient jacinth
Nice!
but thanks
?
i zoomed in
no
How do I calculate only the black area? This is a roundabout.
do you know how to calculate the area of the middle circle
@upper karma
by middle i mean between the black and the white
which one
Both
I tried using the formula for radius and got 4.37 and got it wrong
what is the formula for the volume of a cylinder
V= pie r2 h
so substitute that in
What would be r though?
that's what they want you to find
what's v
Would it be 480?
yep
I get 4.3702
show me your steps
Well I just put it into a calculator but let me try by hand
ok if you want my help show me your steps
Maximo:
$\sqrt{19.1}$
Ann:
@onyx cloud
4.3703
I think I got it wrong because I didn’t round to the nearest tenth
and it says rounded to the nearest tenth
So 4.4
cm
Ok
For the next one I did 4 x 1.2
And got 4.8
But that’s wrong so it told me “if the scale factor is r=4, the volume would be affected by what factor”
L x w x h
perfect
now what if we multiply the length width and height by 4
what would that look like
$V = l\cdot w\cdot h$
Maximo:
V•4 ?
do the multiplications on the right side first
V= 4l•4w•4h
so then what will the factor be?
4?
$4l\cdot 4w\cdot 4h=4\cdot 4\cdot 4\cdot l\cdot w\cdot h$
Maximo:
64?
Ty I have one last question
Max
yeah
Are u done ?
Rip I have canvas too
so now you have that the volume will be v*64
so plug in your original V and you'll have what you're looking for
whats up pulse
i'm boutta go to bed so hope its quick
64 divided by 18.75?
i woke up at 5 pm yesterday and haven't slept since
and also remember i might be in a different time zone
yk why are you dividing
oh lmfao
Idk
Lol
Question 4 isn’t 64 and 5 isn’t 3.41
Then 5 is 18.75/1.2?
That’s wrong tho
which one
ah shit
do the cube root of that
let me explain why though
let me explain why though
Maximo:
$V_1 = l\cdot w\cdot h$
Maximo:
and that is the small cereal box of 1.2
then we have that
$V_2 = sl\cdot sw\cdot sh$
Maximo:
where s is the scaling factor
so then if we plug in the numbers we know
we get
$1.2 = l\cdot w\cdot h$
Maximo:
and $18.75 = sl\cdot sw\cdot sh$
Maximo:
but this formula right here $18.75 = sl\cdot sw\cdot sh$
Maximo:
Maximo:
and then we see the lhw
Mhm
Maximo:
Maximo:
$18.75 = s\cdot s\cdot s\cdot 1.2$
Maximo:
$\frac{18.75}{1.2}=s\cdot s\cdot s$
Maximo:
Maximo:
$s=2.53$
Maximo:
did you get confused by anything at all
No
alright
as long as you understand how we got there
ight pulse if its quick ill help if not i gtg
yeah thats a lil much for me
Dang ok
gl though
pretty easy vector Q but i am a little confused
(imagine below)
so i gotta find the tangent vecotr of this
which is simply c'()
but i also have to find the equation of the tangent line to the given path at the point c(1)
how would i do that ?
the expression for a point on the tangent line is c(1)+c'(1)t
can someone check a and b for me? Also for part c im not really sure how to do it but i drew a diagram, can someone help me please?
how do I rotate an image
oh i will retake it then
,rotate
nvm
oh for the last question you need to know the angle bisecting theorem thing
huh
ok
yep it's right
a is right let me check b
okay
Hey so I have a question for my homework: (cos^(4)x-sin^(4)x)/(cos^(2)x)=1-tan^(2)x ; here is the problem but how would the left side of this problem look like to verify this is true?
Fishraider:
Compile Error! Click the
reaction for details. (You may edit your message)
that gives me big brain damage
the expression for a point on the tangent line is c(1)+c'(1)t
@brittle condor there is no need to compare what i said to the book
there is if i wanna understand what i have in front of me with what you are saying 😛
give it some thought and you'll see they'll get the same points on the line
probably. i just wanted to see. i got l(t) = (t-1, e^2)
could you check or .. ? LOL
@vital frost I got it
i won't check your computation but i will say that c(1) is the point of tangency, c'(1) is a vector that gives the direction of the tangent line, so c(1)+c'(1)t where t is real will pass through all of the points on the tangent line @brittle condor
Thank you for taking the time to help me
do you still need help
yeah
do you know what $sin^2x+cos^2x=$
Fishraider:
that would be 1 correct?
yes
did you do that before?
if you didn't then you will solve the problem knowing this
ok I believe i understand
can somebody help me with a quiz?
thank you
yes what is the question jett-
asking for help during a quiz is a bannable offense
i thought it's only for exam
i got a different answer with ur way (a neg sign isntead of pos)
volume
sorry I meant volume
jett, you're taking a quiz right now in class?
well area of circle*height=volume
no, its a homework assignment, im doing online but I dont understand
so what did you mean by "quiz"?
if you know the area of the circle then you will find the answer
area of circle*height
tbh if he wanted to cheat he literally could've searched up volume of cylinder calculator
i dont get it
let me try the question
alright
so far I got AE = BD with congruent triangles
o how
OH
I got it
ok
so you actually don't need the angle bisector theorm after all I was small brain
label the angle abd theta and try to come up with as many angles as you can
@visual mist
you should be able to see many similar triangles
(that are most likely congruent but I haven't proved them yet)
can you show me your drawing
neat
do you see ACE and BCD
ye
how are they related
about the triangle
wdym
Can you prove Ace = bcd with SAA
i think so
wait let me draw it
well ok AC and BC is the same because ABC is an isosceles triangle, they share angle c and angle DFA and EFB is the same because they are vertically opposite
okay
wait
im not really sure, but angle DFA and BFE is the same because vertically opposite, DF and EF is the same, and FA and FB is the same???
you don't know df and ef are the same
tru
just prove that afd and bfe are similar and after we will find a side length which will prove they are congruent
and you do need the angle bisector theorem
wots the bisector theorem
you have to search that up
is he online
I mean you can also ask him how to do it
maybe he doesn't need to use that theorem
now you can prove those are congruent with SAA angle
ye
wait isnt it SAS because angle DFA is the same as EFB and then FA is the same as FB and AD is the same as EB
yes you can say that too
and also u said abd is equal to bea is it because they share AB and DAF is the same as EFB and then they share AFB
ok
my brain is going to explode but I hope I what you wrote matches up with what I think you wrote
it's just about proving similar triangles to congruent triangles with Angle Side angle
overcomplicating the problem
u have better way?
look at the info given.
the base angles of the isosceles triangle are bisected right?
yes
it shouldn't be too bad all we did was we proved EB=DA with ASA and then proved ADF = EBF with ASA
hahahahaha ye
which means those 4 angles formed at the base are equal right?
yes
specifically ABD and BAE
ye
hmm
and what type of triangle would that make (Tri)ABF
yes
then wot
and then apply a theorem related to isosceles triangles
something relating sides to angles which you had already used when constructing your diagram
in short: the sides opposite equal angles of an isosceles triangle are what?
wdym
specifically ABD and BAE (are equal)
in your triangle ABF,
which side is opposite angle ABD
no
in your triangle ABF
perhaps if I labelled it as angle ABF instead (which is still the same angle)
idk
try not to overthink it
focus only on the triangle ABF
and you can pretty much ignore everything else now
and?
specifically ABD and BAE (are equal)
mhm
those are the base angles of that triangle right?
yes
2 ab?
no? also why's there a 2 there
u repeated AB twice
side that isn't touching
is what it means for a side to be opposite an angle in a triangle
well AB and BF are touching ABD
so the side that isn't touching is:
u gave me the sides AB, BF and BF.
AF then
similarly which side is opposite angle BAE
BF
and from the definition/properties of isosceles triangle, would they be equal?
the angles or the sides
well we already established that the angles were equal earlier
because the angles are equal, would those specific sides also be equal?
and that's it
what is csc of that theta
i got -17/8
because i drew a triangle from origin to -8,15 to the y axis
what's the definition of csc?
and what is the length of the opp side
that sthe problem
idk where the triangle is formed
is it from origin to 8 15 to x axis
or origin to 8 15 to y axis
draw a vertical line from (-8,15) to the x axis
wait why there
isnt the angle on the other side?
if thats the real angle, then the csc should be 17/15
i got it from the angle of the x axis to y axis and then opposite over adj
that look ok
wait
but it doesnt seem right
yeh
@silent plank but
can u explain
why its not the other angle
because its asking for the theta
look up stuff like reference angles
Is this system check right in saying that my work in wrong?
I did the equation
cos8x-cos2x = -2sin((8x+2)/2)sin((8x-2x)/2)
lol rip
i kept double checking every single sign making sure they were right but didn't stop to do the signs right
thanks
@upper karma what extra measurements can you determine from those diagrams?
Goniometric
it's an actual word, but I have no clue how it comes into play here