#help-39
1 messages · Page 103 of 1
Did you try to extend the two parallel lines in order to find equal angles and deduce the bearing ?
Moreover, if we write B(A,C) the bearing of A from C, you can notice that $B(A,C) - B(C,A) = \pm 180^\circ$
RedxClaw
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What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
I multiplied and divided by the conjugate
but dunno how to proceed
I mean we can cancel some stuff out
but after that what?
,, \lim_{n \to \infty} \frac{\left(\frac{3^n}{5n} + 2\right)}{\left(\sqrt{\frac{9^n}{n^2} + \frac{3^n}{5n} + 2} + \frac{3^n}{n}\right)}
938c2cc0dcc05f2b68c4287040cfcf71
,w lim n to infinity (2n)/(3^n)
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how to do number 6
?
ok i see
so the vertex should have been (-5,-38)
what is vertex form mean thou gh
you mean y=a(x-h)^2+k?
yes
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Hi I need help ^_^ I'm in an undergraduate formal logic course right now.
Are the two statements "G and J will not both do it" and, "G and J both will not do it" logically equivalent?
I want to express both statements as ~(G & J). Looking for some feedback on this because I feel like statement 1 implies that both will not do it, leaving room for one to do it. Statement two says that both will certainly not do it.
Ty
It’s a little vague to me, linguistically, but I’d take the first statement as an xor statement (exclusive or) and the second statement as a neither/nor (negation of or)
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Can someone explain how to manipulate lim --> 0 sin(x+h) - sinx / h to get it into the form where the trig identity can apply.
they told you the trig identity to apply below
you have sin(x+h) - sin(x)
and the identity is
sin(A) - sin(B)
so just apply it
which lets you express your difference:
sin(x+h)- sin(x)
as a product
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This is from MVC, I just want to know why is this the case? I can't intuit it.
Is |x| differentiable at x =0?
I remember it's not because it has slope 1 and slope -1 on both sides of x = 0
Similarly the same thing is going on in this question
Oh the case where the length of the vector is 0 but it has "velocity"?
imagine uniform circular motion
|r(t)| is just length of position which is constant, so left side is 0
but right side, it is magnitude of velocity which is not zero
Oh yeah
in other words, left side is the rate of change of magnitude of position while the right side is magnitude of rate of change of position
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@pseudo mirage Has your question been resolved?
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So my question is this
I get a(1 + i) + b(1 - i)
Which breaks down to two equations
a + b = 0
(A - b)i = 0
I'm guessing with the real part, I drop the i
And a =b=0
But I can't understand what to do over c
what does this mean?
That a and b don't have an Imaginary part over the real field
they don't, but why does that mean you can conclude that a = b = 0?
Because you're left with the system
A + b =0
a - b =0
A = b
basically (a + b) + (a - b)i = 0 for a, b real means that you can conclude both a + b = 0 and a - b = 0
Yeah and then get a =b=0
That's My question
you just need to show linear dependence
are 1 + i and 1 - i multiples of each other?
Thanks for the painful obvious 🙂
Haha have a good day 🙂
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👍
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Let ABC be an acute-angled scalene triangle with incircle ω and circumcircle Γ.
Suppose ω touches line BC at D and the tangent to Γ at A meets line BC at T. Two
circles passing through A and T tangent to ω meet line AD again at X and Y .
Prove that BXCY is a trapezium.
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Can someone tell me what I’m doing wrong? Pls ping me on reply
Please don't occupy multiple help channels.
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help?
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Whats the best website that tells you current currency interest rate AND so I can efficiently change and calculate currency value (e.g. how many 5 euro is in dollar).
@obsidian grail Has your question been resolved?
Does it work with Icelandic kronas and polish zloty?
,w convert 5 isk to pln
@obsidian grail Has your question been resolved?
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so for this querstion i got the asnwer A
so does that mean that if i have log(c)/log(b) thats = to ln(c)/ln(b)
Look up the change of base formula, but generally yes
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.rotate
ive only ever seen transformations
like
x' = -x-3
not x' = -y-3
for the first part i just plugged in the values
x' = -(-5)-3
= 8
y' = -3+2
=-1
(8,-1)
but idk if its right and idk how to describe those transformations
<@&286206848099549185>
lemme look
Have you done a?
yes idk if its right
.
No problem with it
Have you learnt how to describe a function in matrix way?
i dont recognise the name so i guess not
i know that if i have like
Name doesn’t matter
x' = 3x then thats a dilation by factor 3 in the y axis
no i mean idk what matrix way means
ive never heard of it
why 3x+4y?
oh
on the right
thats interesting
is there any other way to part b?
because i didnt learn this way
@latent quail
nevermind I have solved it
thanks
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Ho can soes the cramer method works
why is it urgent?
what's your native language?
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hi can someone tell me how to do this question without using cosine rule?
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Can Somone Explain me how to solve these
faiyrose
the answer is supposed to be only x = -5
my answe sheet is showing x = 5 or x = -3
i dont get it how its -3
ohhh
its +-
sry i missed that point
how will it be -5?
faiyrose
ok i got it
faiyrose
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can someone try to explain this to me
i have not tried to understand it
nor have i been taught it in class yet
this looks easy to apply though im not gonna lie
What don't you understand
They literally just applied the theorem
yeah ive just realised
theres nothing to ask for help with
😭 seems really easy
thank you!
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guys im completely lose on how to do this question, can someone walk me thru it?
<@&286206848099549185>
What do you need to find?
Hint : draw a radius to the tangent line
Notice that this is a cyclic quadrilateral, and that the angle of two radii at the center is double the angle of two lines at the circumference that subtend the same arc
That should be enough for you to try and solve this problem on your own
But let me know if you need more help
what does subtend mean-
It basically means that the two radii touch the ends of the lines from the circumference
Lmao
its 50 :)!!!
Yea there you go
tyty
Np
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in this case why do i need to multiply -2^1005i with 1 instead of i * 1, in this example, is it a situational thing or?
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Any random variable X is dependent of itself right
Unless it's constant
Since P(X=x,X=x)=P(X=x)=P(X=x)*P(X=x) if it's constant
But if it isn't this equality doesn't hold
Yes
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how do you solve sin5theta = -1/5 what will be the theta values
You can’t solve it without the help of calculator
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is there a parametric to cartesian conversion tool like symbolab or any python library doesn't matter
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And so, it's me again with my brilliant questions. So I can't elevate expressions that are equal to 0 to the power of (-1)?
no
No what?
This is the degree (-1). I thought the expression would remain equal to itself.
Ig he meant "no you can't "
Do you mean a =a^-1?
Oh, I assumed that this expression is x.
well x does not equal x^{-1} in general
x=a
1/x=1/a.
Some like that.
Oh
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Does anyone here know Vector calculas??
several people do
!da2a
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question! See https://dontasktoask.com/
Is the solution correct?
think you made a mistake when computing the 2nd and 3rd components
your work is difficult to read; what is the derivative of x^2 + xyz wrt z?
is that the case?
Yes
Yes the third value is differentiated wrt z
are you saying that $\frac{\partial }{\partial z} (x^2+xyz) = xyx^2$?
Bair
Yes
im very confused, we can first apply linearity and differentiate x^2 and xyz separately, x^2 is constant with respect to z, so it's 0 when differentiated right?
then xyz is just linear, so when differentiated it's xy
@primal sorrel Has your question been resolved?
@ocean hornet is it correct now? I think i messed this question up. Cux i was applying chain rule to solve the gradient of a scalar in a previous question
Anyone?
Yeah I think looks good
Thank u
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- Let ( f : \mathbb{R} \rightarrow \mathbb{R} ) be a differentiable, non-identically zero function that satisfies
[ f^2(x) = \int_0^x f(t) \frac{\cos(t)}{3 - \sin(t)} , dt. ]
Calculate ( f(0) ) and ( f(x) ).
938c2cc0dcc05f2b68c4287040cfcf71
$f^2(x)$ representing $f(f(x))$, right?
@merry carbon
@stoic imp Has your question been resolved?
pressumibly
im sure it doesnt mean second derivative at least
because that would be (2)
so its
g(x) = x^2
f o g(x) = g(f(x))
function composition
Yea, it's most likely not (though often that notation is used to mean (f(x))^2 instead, which is "interesting"
)
😼
I think in either case, I’d use FTC sure 
ftc1, ftc2, ftc3
(Actually on thinking about it, more likely to be (f(x))^2 they mean)
“The one which has the integral you see in it”
(I never remember which order they’re in tbh)
The first one from here
You have immediately f^2(0) equal to 0 innit ?
its fundamental theo calcukus
I just don't know if it is f(f(x)) or f(x)^2
So, f(0)^2 is 0
?
'cause you will integrate from 0 to 0
non-identically zero function
Now you have a square equal to 0
Mayyyyy we think and admit that a real who squared is equal to 0 CAN BE 0
😂
ok
?
,, f^2(x) = \int_{0}^{x} f(t) \frac{cos(t)}{3-\sin(t)} dt
Oh
938c2cc0dcc05f2b68c4287040cfcf71
now what
And on the right
,, \frac{d}{dx} (f^{2}(x)) = 2f(x) \cdot f'(x)
938c2cc0dcc05f2b68c4287040cfcf71
And now use the same idea for the left, but with your theorem
,, 2f(x) \cdot f'(x) = f(t) \frac{\cos(t)}{3 - \sin(t)} dt
938c2cc0dcc05f2b68c4287040cfcf71
yes but do not use t, is is x on the both sides
$\text{Let F a primitive to} f(t) \cdot \frac{cos(t)}{3-\sin(t)}$
so you will have the integral equal to F(x)-F(0)
938c2cc0dcc05f2b68c4287040cfcf71
,, 2f(x) \cdot f'(x) = f(x) \frac{\cos(x)}{3 - \sin(x)} dx
how is that change of variable possible
I just explained it
.
938c2cc0dcc05f2b68c4287040cfcf71
In your opinion ?
is this a diff eq?
do you think it is ?
,, f'(x) = \frac{\cos(x)}{2(3 - \sin(x))}
do you find it similar to what you've seen in class ?
you got it, now what in your opinion ?
938c2cc0dcc05f2b68c4287040cfcf71
finding the integral
how
dragonrard
sin and cos you know
oh, we can u sub you mean
?
u = 3 -sinx
may be yes 🙂
u' = -cosx
938c2cc0dcc05f2b68c4287040cfcf71
?
cos(x) = u'
-sin(x) = u?
but d/dx -sin(x) = -cos(x)
,, \int \cfrac{u'}{u} = ln(u)
dragonrard
-cos(x)
it's really close to our result don't you think ?
if you have a problem with the sign MAYYYYY you just add a - on the beggining
,, -\ln(3- \sin(x))
sin is bounded $-1 \leq sin(x) \leq 1$
938c2cc0dcc05f2b68c4287040cfcf71
so in your ln everithing is negative. not defined
938c2cc0dcc05f2b68c4287040cfcf71
what is the answer
,, f(x)= -1/2\ln(3- \sin(x))
dragonrard
,, f(x)= -\frac{1}{2}\ln(3- \sin(x))
938c2cc0dcc05f2b68c4287040cfcf71
i think
lmao
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thanks
You're welcome
ok
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@drowsy flare Has your question been resolved?
<@&286206848099549185>
@drowsy flare Has your question been resolved?
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Did I do this right
The 20% bit yea
(because that comes from the question)
for the other numbers, nope
why would 20% of the total, at 1500, be larger than 30% of the total (which you've said is 480)?
Thought I could use the first number to calculate the rest
Wait would it be divided
@dapper orchid Has your question been resolved?
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does anyone know how to approach this rotational motion physics problem?
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in this triple integral, can I change the order of the integral into dy dx dz and move around the bounds
cause someone told me I cant but i thought I could
you can change the order of integration but you would need to change the bounds to match (bounds can only depend on the outer integration variables)
uhhhhhhh
this is the original problem right, and hypothetically Lets say I wanted to do dy dx dz
hey im so sorry to interupt but i have been sick in my school for ages and i have no clue about the upcoming exam can you please helkp me with some specific topics
for the problem I put in
.
hypothetically lets say I wanted to do dy dx dz
which should still be mathematically logical
doing dy first, I can say that the bounds of y go from 0 to x
then how would I find the bounds of dx
...
okay no probs
.
not quite
oh
sorry im having a hard time with this concept (no pun intended)
so what would be the bounds of dy
we are imagining allowing y go from smaller to larger, and finding which surfaces it passes through along the way
right, in that case wouldnt y go from 0
but it would end at where y = 0 intersects with z = 4-y^2
right
right
if we quantify it by that
y is decreasing
cuz if i draw it out
it would look like
sorry that took so long, I was tryna find out why it didnt work
therefore the bounds would go from 0 to x no?
but i gave that answer and it was wrong
remember that the bounds may depend on x and z
i mean
but also notice that in increasing y, we enter the surface at y = x
right
from my observations, its either bounded by y = x OR y = sqrt(-z+4)
so then would it be bounded between 0 and y = sqrt(-z+4)
i think that would be it right
<@&286206848099549185>
ok so apparently the integration is y = x to y = sqrt(-z+4)
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maybe you can better visualize with this: https://www.desmos.com/3d/4xmhrcej7v
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How do I do this?
I got the r value to be -0.3084 but for the second calculation, I keep getting the wrong answer
Never mind I figured it out
I just did the calculation wrong
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The average monthly temperatures in Chicago can be modeled by a sinusoidal curve. The minimum average temperature is 27.2 (degrees) and occurs in January while the maximum average temperature in August is 73.7 (degrees). a. Let January correspond to x=o, Write an equation in the form of y = acos(bx) + d that would represent the situation. Show your work.
Okay so i'm preparing for my Trigonometry final and forgot how to do this.
I know that January is the minimum and x=0
so naturally, this would be sinusodial.
But the problem asks us to write the equation in cosine
that makes sense
because cos(x) = 1 when x=0
so you can put the amplitude in front to stretch it to the temperature it needs to be at t=0
the amplitude is half the distance between the min and max temperature
so A = (73.7 - 27.2)/2
what is that @tepid panther
so just to recap
to find the amp. you did max-min./2
I understand that
and cos(x) = 1 when x = 0
so that's why we're using cosine
yeah becasue the temperature isn't 0 when we begin. this will save us from needing to phase-shift the graph
ok
well hang on a sec
first we should shift the graph up or down so the transverse axis is where we need it
tranverse axis?
midline of the graph
one sec
oh
the problem is that I told you to subtract
I know better
sorry
we are averaging
(min + max)/2
okay so amp. would be max-min/2 and mid. would be max+min/2
alright
glad we cleared up the confusion
midline is 50.45 and amplitude is 23.25
f(t) = -23.25cos(bt) + 50.45
good job
b tells us how to scale the graph horizontally
recall first that the period of standard sine and cosine functions is 2pi
for cosine, we begin at the max when t=0 and reach the min when t = pi (half the period)
oh
and we want our function to be negative in front
why?
because -23.25cos(0) + 50.45 = 27.2
and -23.25cos(pi) + 50.45 = 73.7
we needed to start at the min and reach the max in half a period
now, the time between january and august is 7 months
so the full period is 14 months (sort of...temperature graphs, if you have seen them, are not perfect sine or cosine waves)
thus, b = 2pi/14 = pi/7
i think I understand
I understand this
well understand that it couldn't actually be 14 months or it wouldn't reset next year
but let's make sure this works
since I've already goofed twice at least
right
f(t) = -23.25cos[(pi/7)t] + 50.45
We can test this works in Desmos
success
so, recap:
We wanted cosine instead of sine because when t=0, we have a nonzero value. This saves us from having to calculate a phase shift.
f(t) = a*cos(bt) + k
first we want to find where the graph is centered (vertical shift aka transverse axis, "k"). That's the average of the highest and lowest point.
the amplitude "a" is the distance from that centerline to the highest or lowest point. Choose the sign that makes the graph start where it needs to
These problems give us the extreme points, which are ALWAYS a distance apart of half the period. So, the period of the graph is twice whatever that distance is
that means b = pi/(the distance between the extrema)
or more generally, 2pi/(twice that distance)
I pretty much understand everything but why the amplitude is negative
can you re-explain?
yeah
so from the midline, it's the same distance to the max as the min
right
when t=0, the graph is supposed to be at the min
so we need to SUBTRACT that distance from the midline
no, this does not make it a sine graph
check it out:
cos(t) + 1
let's say when t=0, we are at a max of 2, and when t = 2pi, we are supposed to be at a min of 0.
why would we be at the min if the period is 2pi?
hang on I flipped it to be simpler
more like the standard cosine function
oh okay
this is a standard cosine function with a vertical shift of 1
lol, I had to fix it again
this is like your tenth mistake 😆
I know
I'm cursed 💀
but I've been doing this longer than you'd think
ok the constant number we added, the 1, means the center of the graph is at y=1
the standard cosine function begins at a max of 1 and goes down to -1
(at the halfway point, when t=pi)
so actually, if we change nothing, we will start at the max of 2 and end at a min of 0
because cos(0) = +1, and cos(pi) = -1
+1 + 1 = 2; +1 -1 = 0
do you understand that?
now say we had to start at the min and reach the max after.
then we just have to multiply cos(t) by -1
and that will do it
the bold part is really the most important part, and that's all I'm really thinking about when deciding if I need the cosine term to be positive or negative
"from the midline, do I need to start above or below that line when t=0"?
above -> +
below -> -
@tepid panther does that help?
hold on
so if the function is at its minimum when t=0 from the midline, we'll subtract the amplitude and when the function is at its maximum when t=0 from the midline, we'll add the amplitude?
exactly that.
I don't necessarily understand the theory behind it but I understand that i need to do that.
Okay.
it's because cosine oscillates between max and min (or min and max if it's negative)
(as does sine)
we MUST shift our graph up to the midline
and then just figure out if we start with the max or the min
this case was the min
it helps to draw a picture.
yeah
so the way I would have done it:
here is a graph of average temperatures over a year:
wait continue your thing
well, I'm basically done with that
but I was saying earlier the period obviously can't be 14 months, since there's only 12 months in a year
this is the typical shape of average temperatures we measure
right
it's concave-down as we approach the peak (dumps water), then concave-up (holds water) notice the curve is sloped differently on either side of a peak or valley
(fun-fact)
did you have a related question?
where's the fun fact?
cool 
so the way i do it
I would subtract 23.25 from the maximum to match the sinusodial function
that's the way I usually look at it
but this makes more sense to me
I am glad you can understand a problem like this multiple ways!
b. Determine what the amplitude means in the context of the problem
c. Use your equation to predict the average temperature in October ( x = 9)
I'm curious what you think it means?
think about what we used it to do
it took us from the minimum to the maximum
so |a| is the magnitude of the most dramatic temperature swings from the (blank) temperature;
a is negative because (blank)
start with the first part
the absolute value (unsigned size) of a represents the most dramatic temperature swings from the (blank) temperature
okay, the absolute value of a represents the difference in temperture from the average between both the max/min (midline) to either the maximum or minimum
the question asks for a cosine function and the function is at its minimum when t=0 is from the midline, so we'll subtract the amplitude to match the functions
mm...kind of
yeah i didn't really hit the nail on the head
simpler: just say we had to start with the minimum when x=0 whereas the standard cosine function begins at the maximum, so we negated it
i like that and actually understand it
oh good
life tip: don't drink diet soda
and especially don't drink 2 liters every other day for 10 years
what else we got
oh, ok
calculate f(9)
and as a bonus, do you think this will be an under-estimate or an over-estimate of the actual temperature in October? 🧠
I was right that time
buddy threw in life advice 😆
keep your short-term memory
def an underestimate
climate is getting hotter
this is true
but this is not
recall that our model has a period of 14 months
but there are only 12 in a year
right
we need the temperature to be back at the minimum when t=12
right
but that won't happen until later, when t=14 (hypothetically)
right
so the temperature is higher than it should actually be when t=9
sine and cosine functions don't perfectly model temperature patterns
(although a combination of sines or cosines could be artibtrarily close)
so just plug in 9 for t here to get the temp. for october?
I think the way our teacher does it is to have us use a graphing calculator
pretty hard to do w/o a table of values
huh?
yeah
of course
why do you need to graph it?
I was thinking of a previous problem where we're given just a chart of values and we need to find an equation
sorr
but was my thinking right here?
yeah
Reminds me of this hilarious line from Meet the Mathematicians:
"You can model almost any smooth-continuous function with sines and cosines"
"I have smooth-continuous curves, Greg. Can you model me?"
np
greatly appreciated
I have more questions but its getting late.. can I shoot you a message tomorrow?
thats fine
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@lofty finch Has your question been resolved?
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hi, i wanted to ask if i find a parameter in the angle and like thats my answer, do i write 180-(said parameter) for the value (incase its an obtuse triangle) or do i just leave it at that since the reason for doing 180-Shiftsin is because the calculator only returns one answer for an angle which i know the values of
sorry if this is hard to read
whats the question?
I don't think you necessarily have to do it, but your calculator might require you to do it to get the right answer
remember to check if you're calculator is using radians instead of degrees.
no question just theoretical
want to make sure incase something like that is in my exam
nono you didnt get me i meant like
sin(a) = x
a = (coefficient of x) * x
that returns me the angle of a single angled triangle
so in case of an obtuse triangle is it 180-a ?
the 180-a when you show how you solved it. the answer should just be an angle
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what does it mean that we assume elements of logic?
what are the basic building blocks of logic, and what are those made of?
and can implication p -> q be further abstracted?
how to think about implication with linear algebra?
what is the point of the last two rows of the conditional? do we use conditional and implication interchangeably?
F T T
F F T
it was very interesting to see that moving from the philosophical implication that includes "conditionality" and "causality" to one that only includes "conditionality" - seems to be a step towards abstraction
are there resources that explain this? 🙂
@void grail Has your question been resolved?
what are those operators made of?
Not made of anything to the core they are abstract, but the can be made real using transistors.
This electronics video provides a basic introduction into logic gates, truth tables, and simplifying boolean algebra expressions. It discusses logic gates such as the AND, OR, NOT, NAND and NOR Gates. This video is for college students who are taking introduction to logic design.
Full 2 Hour Video on YouTube: https:...
Logic gates can be made out of mechanical systems it can be made of transistors and the flow of electrons. But is still an abstraction https://en.wikipedia.org/wiki/Boolean_algebra
In mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variables are the truth values true and false, usually denoted 1 and 0, whereas in elementary algebra the values of the variables are numbers. Second, Boolean algebra uses logical operators such ...
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how would i do b?
Apply the formula you have been taught for compounds interest
yes but for this one the money is also been added anually
and compunded monthly
And the formula you have been given that shouldn't be a problem
Idk either since you just gave an answer
well i did
a1= 300
a2= 300 (1.003)
a12= 300(1.003)^11+300
a252= 300(1+1.003^13+1.003^23....+1.003^251)
and used sum
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i dont understand the transition between the 4th step to the 5th
how does 3x+6/4 turn into that
(3x+6)/4 = (3x)/4 + (6)/4 = (3/4)x + 3/2
what
So we can split the numerator into two fractions since it's addition
Suppose we have a whole fraction, that being 1/1 = 3/3, right?
yes
yea sure
Which is still equal to one
yes
We do the same thing here
The reason we do it is because we want to isolate x
We want some number "a" times x by itself, plus another number "b"
so the number next to it is the graident?
That's correct
i just cant figure out how to split them up ivetried
yes
So we can split it where the + sign is
okay but how do we do that
How? Well it turns into two separate fractions, being 3x/4 + 6/4
oh i dont know if i understand it fully could u help me through a question please
Sure
perpendicular to y=-2x+9 and has a y intercept of 4
first we find the graident right
y=mx+b
yes a little i dont understand it
There's an easy way to find the gradient of a perpendicular line
what is it
m_1 * m_2 = -1
how do we do that
If this isn't method your teacher wants you to use, then there might be another method
How were you taught to solve this problem?
i wasnt there rhe day it was taught however on the formula sheet given
it says m^1 times m^2= -1
i dont know what that means though
m1 and m2 are the gradients of the lines
yes
For example, m1 = -2 in the problem you gave, and m2 is what we want to find
How would you solve for m2?
Not quite, we only need m1 * m2 = -1
then how do we find m^2
Do we know what m1 is?
If we have 1 equation, we can solve it if there is only 1 unknown
Correct
so -1 divided by -2 is m?
That is the gradient
1/2
m1 and m2 are the gradients of two different but perpendicular lines
so we need to find m^2 to find the graident?
The gradient is m2
how do we find the equation
Well, in the equation y=mx+b, what does "b" represent