#geometry-and-trigonometry
1 messages · Page 186 of 1
Not sure how to calculate CD if you dont have an angle value
Also you can use Law of Cosines to find LW
Yeah and did u get 4.3?
LW^2=5.1^2+5.1^2-2(5.1)^2cos(50)
Or better yet law of sines because of isoceles
== sind(65)
sin(13×π/36) = 0.90630778703665
Ye I used sine
==sind(65)/5.1
10×sin(13×π/36)/51 = 0.177707409222873
==sind(50)/(0.177707409222)
500‚000‚000‚000×sin(5×π/18)/88‚853‚704‚611 = 4.3107062697763
Yeah 4.31
Look at the triangle with 50° in correlation to LW
Which im not sure what to do
What's the max value for LW if you were to make the angle as big as possible
🤷
cant you just use the triangle inequality
and the reverse inequality
to find the range
I'm pretty sure
instead of whatever ur doing, pjs
@chrome fiber yeah I asked other people and they said they used sine
Which we have not learned about
yeah no
Yet
yeah so what do I do to find it without sine
for a triangle with sides $a, b, c$, the range of any side is given by $|b - c| < a < b + c$
june:
triangle inequality basically says that the length of any side of a triangle is always going to be less than the sum of the other two sides
reverse inequality says that the length of any side of a triangle is always going to be greater than the absolute value of the difference of the other two sides
idk pjs, you were confusing the poor guy
And she just went over it fast because it was going to be thanksgiving break
so suppose you have a triangle of sides a, b, c
take side a
triangle inequality says its going to be less than sum of the other two sides
So I'm shaky on how to get CD, DL, and LW
which is b + c here
so you have a < b + c from that
reverse one says
any side will be greater than absolute value of the difference of other two sides
so take a
absolute value of difference of other two sides is |b - c| or |c - b| (order doesnt matter here)
so a > |b - c|
you can combine those two inequalities
$|b - c| < a < b + c$
june:
uh brain is hurting
Notice that if you were to make that angle of 50° all the way out to 180°(but not yet 180 due to it still being a triangle), it would approach a line segment of the two sides added together
And vice versa with making your angle approach 0 will allow LW to be the two side lengths subtracted
So, In ACD 4.2 - 2.5 < CD < 4.2+2.5
The answer would be nice
0<LW<10.2
Is that for the ABC part?
Well C as a compound inequality
Upper bound for length of LW is 10.2 so LW<10.2 for a
Ok
And LW>0 for lower bound
So how would you find CD and LW without Law of sine and cosine, and what are the answers @keen aspen
You cant really
Unless the triangles were right
You could use pythagorean theorem but nope
so u do nothing?
Well you can find the length but not without trig
Yeah how do u find that
Or is sine the only way?
We got another one to do also
But it doesn't have more steps to it
It's just solve
PR also 1.9
Yes
I'm guessing RJ 1.7
JM and MV not sure
@chrome fiber could probably help on this one?
Yeah maybe June can find the lengths, idk if its possible
which ones?
Oh wait maybe I'm stupid
Recent Post for JM and JV
its asking for a range
Yes
just use what i told you
KMJ could be 28° maybe?
$|b - c| < a < b + c$
june:
for both of those triangles
Oof range lol nvm okay yeah
That's what I'm supposed to use for the 1st too lmaoo
Answers would be nice like I said
Wow I need to read questions better
Look at PR
Uh huh
So MV the longest ranglr would be 4.8 and the shortest would be 0.6
@keen aspen yes?
For rj idk what to do
Ok
And now JM
And JM?
Now add up all the lowest bounds
And add up all the highest bounds and thatll be your range
Lol
I really appreciate y'all helps @keen aspen @chrome fiber
np
life savers lmao
@clear haven I ended up doing something like this
Does your method with vectors do something like this?
"Show that x^2 +y^2 = r^2 is orthogonal to y = mx. Conclude that the family of circles centered at the origin is an orthogonal trajectory of the family of lines that pass through the origin. Note that there is a technical issue when m = 0. The circles fail to be differentiable when they cross the x-axis. However, the circles are orthogonal to the x-axis. Explain why. Likewise, the vertical line through the origin requires a separate argument."
Do i just plug in some numbers for x and y and graph it or is there a formula i don't know of?
Please some help
wait wat
so what's the question
do they want you to prove that the circles are orthogonal to x axis
@left folio you have to show that the slope of x^2 + y^2 = r^2 times the slop of y = mx is -1
Since y'=-x/y i understand that but how
an intuitive approach would be to think of all y = mx as all every straight line passing through the center and since the circle is centered at the origin, every single line must be a radius to the circle
which is always tangent to any point on the circumference
from (I)
$y' = -\frac{x}{y}$
june:
june:
what's the product of those two?
Sorry but the product of what exactly
the two slopes
@chrome fiber I see that m is the slope in the equation y=mx but i don't see any other slope in the equation y'=-x/y
Sorry if i sound stupid but i don't know
@sick veldt use another question channel below
@left folio well yeah
so, the slope for the circle is y' = -x/y, right?
Yeah
Do i count them both as functions?
so m = y/x
And multiply using the function's rules and so on?
not the circle
ok
but anyway
so for
slope circle = -x/y
slope of line = m = y/x
you need to prove that slope of circle times slope of line = -1
for orthogonality
Mmmh i understand
in terms of tan x
how does cos(90-x) = sin(x) go to 1/tan(x)
thanks what about the 4d)
well you know sin and cosine are periodic functions
so you can subtract 360 from the functions argument
is the arg the brackets rihgt
the argument is what's between parentheses
so sin(540-x)/cos(540-x) --> sin(180-x)/cos(180-x)
right
what now
ill try but im pretty retarded on this topic
lol
well it's just about applying formulas
do you have some formula in your notes
that could help?
is 4d tan(-x)
the book says -tanx but im assumin tan(-x) is the same thing
yea thanks a lot i finally understand this shit
tbh the topic is acctually fine its just those questiosn which confused me the fuck out
As a visual person I find answering questions like this easier when I look at the graphs and try to figure them out
yea i plot them on desmos
@last pollen the -360 thing for the last one, does that work for the
would that work for them all
yes
all of them are periodic functions
and yes tan is an odd function
so tan(-x) =-tan(x)
this comes from tan being the product of two functions
one is even the other is odd
so you get an odd function
sin(x) is the odd one
cos is even
ok so the first one is 1/tanx , but if i minus 360 from sin(90-x)/cos(90-x) --> sin(-270-x)/cos(-270-x)
and then do tan(-270-x) --> -180 --> tan(-450-x) --> ?
@last pollen
that doesn't help much
it's not wrong, but won't help you with this excercise
you should follow blah's advice and make a drawing
I see you cardi 👀
@jade solar my method with vectors is slightly related but is very very different
just dw about it haha
how is tan(270-x) --> 1/tanx and tan(360-x) --> -tanx!
mostly but right AC = AC
because cf is an extension of ac
but AC is the actual sides of the triangle
@lament bay
Oh my bad thanks!
and DAC and BAC should be congruent by substitution
Really?
yes
How and when should I use substitution property?
ok so (this might take some time to type):
After vertical angles
<BAC ~= <CAD
~=*
by that I mean congruent
Can you help me on #2?
So if shapes connect within each other via lines? It always means reflexive ?
yes for the segment that is on both triangles
Wait @keen aspen how do u her CD DL and LW again?
@lament bay after Ef = Ef:
De + ef = cf + ef
Add what and what
Segment addition postulate?
I still don’t get when you use substitution
let's say for example:
@vital frost your range
Yes
LW is from 0 to 10.2
How do I know on a triangle tho?
Use it after you use addition property to combine shorter segments into a longer segments
So it almost always comes after segment addition postulate?
So DL and CD @keen aspen ?
Would it be 4.8+3.1 and 4.8 - 3.1
@lament bay use the article above
Yep
Ok give me a sec
Yep!
brb
Ok cool, thanks
@glad ocean I’m really bad at this 😦
I always never know the next step after given lol
Like I don’t see the angles or theorems I guess haha
@glad ocean so what should I do for the next step?
I don't think you technically need the rest of that to prove AB = CD
B and D are both given to be right angles, so A and C must be right angles as well
Which makes this a rectangle, and we know opposite sides on a rectangle are equal in length
Or, since BF and ED are equal, that means the hypotenuse for the 2 right triangles are the same, which means the lengths are going to be the same as well
wh
So 140
Yes
thank you, I’m helping my friend out with their math work.
I just didn’t understand it cause it’s work for a couple grades above me
And you decided to agree to helping him?
well like I don’t want her to get bad grades cause they’re cool as heck, they asked the server I’m in and I decided to step in and help.
what have you tried?
meme question?
Well you can, but you have to use protractors and stuff
you cant find the value of the angle opposite of x
actually maybe you could make a simultaneous equation
unless the one im thinking of are equal
okay actually neverind
40+x+50+y+(20+60+50+30)=360
x+y+70=180
welp nevermind
these 2 are equal
@chrome fiber " For k ̸= 0 and c ̸= 0 show that y^2 −x^2 = k is orthogonal to yx = c. In the case where k and c are both zero, the curves intersect at the origin. Are the curves y^2 −x^2 = 0 and yx = 0 orthogonal to each other?" Sorry for the @ but i'd like to know if i can just say that they're not orthogonal because their product can't be -1 or what else?
If the product of their slopes is not -1, then they’re not orthogonal
Assuming ofc that both slopes are defined
Thanks again, sorry for the @ again 😃
someone please help me, i have no idea how to do this
A 8,-6 and B 5, -2 are 2 points in what retion does the line 6x - 8y - 71 = 0 divide [ab]
plsss :(
yes iirc what a centroid is
yes 96$
yes maybe consider trusting yourself also
k
yas
ye
kk ty
Use the sin(a+b) formula, find sin x using sin^2 + cos^2 =1?
Can I use trig
B is bisected from BF, that means if you were to extend BC and AD into transversals, you can say that EBF and AFB are congruent from alternate interior angles
sinx=0.40
i get 0.41 for the first
how can i find the other angle
apparently the answer is 2.73 but how do i do it
$\sin(x)=\sin(\pi-x)$
lemon catto:
How do i make this 1-2sin(x/2) equal to 1-sinx
Someone help me on 5-7
sure @torn linden
so do you know what the angle of elevation as opposed to angle of depression means?
i believe the wording is what causes the problem for you right?
@torn linden
No no
So I think #5 is correct
I know that I'm using the correct function on #6, but whenever I set it up I get 0.65
Which is wrong
I'm also confused on #7
Wait lets start with 6
Ok 7
So far I have this?
Yeah
Yes
yeah
ok can we do 6?
ok
yes
and angle?
and you want to solve for x?
yes
yes
then what is the question?
but when I solve I get 0.65
yes
and that angle is 72 deg?
yes
and which trigonometric expression combinds opposite and nearby?
tan
so its tan(72) = 2/x?
you need to read up on SI prefixes
Yeah
ok
ok?
yes thanks
lol
well
you dont have to involve the hypotenuse
which means to fastest way is to use tan
the hypotenuse is just a vector in this case
of the shortest distance
So it is tan right?
well you have nearby
thats the distance between the buildings
nearby = that length u got (forgot what it was)
and x is the delta in height between the buildings
which means
tan the angle of depression
= x/distance between buildings
then solve for x
ok thanks
9 Lie (?)
ah It's 9
I doubted my answer for a second
You can actually take the ratio between the two segments and not the full sides if I recall correctly
this is equivalent triangles right
omar23:
If you would like, you can solve it by cross multiplication after simplifying 12/8 to 3/2:
wouldnt that be assuming the hypotenuse is the same as that base
Oh thanks
still is 9 though apparently
omar23:
Viola!
But you have a good point
When I was his age I was taught that this is a stupid idea, yet it works in some cases.
or so I remember
20/(6+x)=12/x
I initially deleted my answer of 9 because I did this and I remember it might be stupid
Thank you so much!
oof

What year are you in
9th
lol
I’m taking stats next semeter
semester*
I wonder why I don’t take algebra 2
🤔
You didn't take algebra 2?
nop
ABD
Tf
wait
But ABD is only half
I think that's a lie
Lol
Lol
Oh wait we're not bound by the smaller triangle
Nope
I support BDC
LOL
Which isn't even an answer choice
LOL
pair of idiots working on something so simple
Yeppp
I wonder how I even got into this class
Everyone in my class has taken geometry A
I’m stuck learning geometry b without learning any of part a
I support that idea
I was looking for the same thing
instead of my useless mental alignment
you just have to see which letters correlate with which one
Lol
distributive property
fundamental to your success in math

(a+b)(a-b) = a^2-b^2
@supple haven
no
you shold get 1-cos^2
distribute the 1
1*1 is 1
-cos
then distribute cos
+cos - cos^2
the + and - cos cancel
1-cos^2
hence (a+b)(a-b)=a^2+b^2
Wolfram|Alpha didn't send a result back.
Maybe your query was malformed?
t!yt How to foil binomials
Use FOIL to distribute two binomials. The FOIL method — which stands for first, outer, inner, and last — takes two binomials and multiplies them for a single...
@quaint ruin What does HL mean?
HL means hypotenuse leg
It’s HL
i misread the leetters
bcuz it correspond
lmaooo
ohhhhhhh crap I see what I did wrong now
i keep looking at the picture wrong
I forgot to include the 1 like a big doof
@quaint ruin Isn't a and b the same thing?
learning
@supple haven
no
bcuz it has to correspond with ABcy
ABC
To be similar
Help with this
I forgot
how to do this
i believe you use pythagorean theorem for that one
ok i need to domy hw
Similar triangles I think
I got 8
Yes it is B
i read ur picture again and i dont think you use pythagorean theorem
idk how u do that
Use the ratios for both triangles.
multiply by 5
the dumb way (my way) was to add 3.5 until I got to 17.5 then count the amount of times that took
so that way I found out 3.6 times 5 = 17.5
so if thats the case then
wait I might be dumb
And this
looks like law of sines/cosines
oof
ez pz
oh shit
i think
ughh
you could also guess and check
since they should equal eachother if they are the correct x and y's
what are the sidelengths for a 45 45 90 triangle?
I know that two of them are rad 2
isosales ?
i have the iq of a small child, you'll have to be a bit simpler
i just dont remember the 3rd sidelength
a^2 + b^2 = c^2
thanks im dumb
<@&286206848099549185>
To prove that both (1) and (2) we have to prove that the angles 1 and 2 are 90 degree angles, since doing so would prove they are perpendicular.
one way I devised to accomplish this is to prove that both triangles are congruent.
- RC = AT (Given.) By subtracting middle segment TC, we can deduce that RT = CA
- SR = AB (Given)
- ST = BC (Given)
From this, we can conclude that for both triangles all the sides are equal, and that they are congruent triangles.
For them to be congruent triangles, all their angles must be equal. Which would mean that 1 = 2, let us label 1 or 2 x.
Since 1 and 2 are supplementary angles, 1 + 2 = 180. Since 1 = 2, We can write this as 2x = 180 or x = 90. Proving that both 1 and 2 are each 90-degree angles. Which would make the sides required to be proven perpendicular.
There you go @lament bay Tell me if you spot a mistake in my work or something you don't understand
@meager lantern yo thanks so much

you can factor that
yas
After that?
when you're solving for x in x(x-1) = 0 (as an example), what do you do?
yus
solve idk?
we actually simplified our bad ass equation with squares with 2 more basic trig eq
if you want yes
seems roight yes
yus
Not sure about this one
I just graphed the ones that the lines touch on
hello
only this and one more left 😛
yas is correct
Last one
This one I'm lost on
Ik I have to use midpoint formula again
but Idk how to find the x's and y's this way
its DF
and DE
I think
halp
how do you find the midpoint of a segment?
use the triangle midpoint segment theorem ?
yeah its jsut Idk how I find it
so lemme guess
for DE
would the x be 1 and y be 4?
that's the coords of D
is the anwser just the midpoints of ef and df
Its on the question
you add them and divide them cause they are endpoints
and we need the midpoints
what do i do lol
add them or no
is it 1, 2.5???
fe midpoint= (-1,2) and df = (-1,3.5)
Looks like (-1,2) and (-1,3.5) to me
midsegment is a line joining 2 midpoints and the endpoints are the coordinates at either end so that must be the anwser
i think
the question said parallel to DE
in the midsegment theorem the midsegment is joining the midpoints of the 2 lines and the 3rd line is paralle which they stated was De
its also 1/2 in length
yeah you got it write
guys i need help
inmediatly
i have a window of a x y dimensions (600 x 400 i think)
and i wanna create 3 random points
what are the conditions to generate those points in order that the circle made by those 3 points isnt bigger than my window size?
@upper karma isn't the largest circle possible a circle with radius 200?
yes it is
well i found something of use: u can directly find the equation of the circle (hence it's center and radius) from the determinant of a fancy matrix
its the second or third answer
would anyone want to make some questions for me in preperations for my math test tomorrow? it's about surface area and volume
Have you searched google for practice questions with solutions?
have you tried applying the cos(a+b) Formula?
yes i got zero as my answer but im not sure
ok thank you very much
Can someone tell me why sine can never go over 1?
@torn linden well, sin(ax-b) (where a, b are constants) can't because geometrically, sine is the ratio of opposite to hypotenuse of a triangle
And the leg of a triangle can't be longer than its hypotenuse
is this right
<@&286206848099549185>
Well you know CF = BF, right?
<@&286206848099549185>
lmfao
Nah. Thanks though
Help me coach
Law of Sines
yes i remember
sin what
sin of that angle
θ
where did you get 15.3333
ah ok
where did you get 356
i thought its 60
cause mins
isnt 356 for seconds
or no
119.2m
Yeah
ty
Np
its better to use them in decimal form
rather fractions
same thing add A and C
then take that answer
180- ?
sin(37.7)/200
That's the common ratio
You can set that equal to each other parts to find what you need
how did you get 37.7
37+(42/60)
Yes
I need help with my Nicolas Cage pong game, I need help finding an equation to find y (I only know soh-cah-toa)
how do I find tan(angle) * dist?
tan(x)=opp/adj
so tan(angle) = y/dist?
Yeah
so y/dist * dist = y?
yes but that's not the point
if you did y/dist * dist = y, that ruins the point; you already know what y is and there's no need for this
what you need is to use tangent and plug in your angle
but tangent is y/distance
yes it is
but in y/dist * dist, there is no point in dividing then multiplying dist since you already have y
what i'm assuming is that you have the angle so to get y, you need to multiple tan(angle) by dist
is this programming? if so then your lang's math lib probably has tan