#help-49

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twilit field
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midnight plankBOT
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twilit field
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thanks everyone

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slim portal
#

3^(2x+2) + 8*3^(x) -1 = 0

midnight plankBOT
slim portal
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$3^{2x+2} + 8*3^x -1 = 0$

grand pondBOT
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カザミ

rain holly
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what is the issue

slim portal
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How to solve it?

rain holly
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substitute u = 3^x

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then it reduces into a quadratic

slim portal
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So $3^{2x+2} + 8*u-1 = 0$?

grand pondBOT
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カザミ

rain holly
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rewrite the first term $3^{2x+2}$ as $3^2 \cdot (3^x)^2$

grand pondBOT
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Deftioon

rain holly
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remember though you should check your answer for u to make sure its in the range of 3^x since 3^x > 0 for all x

slim portal
slim portal
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I got x = -2

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Thanks

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rain holly
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if you get a u = negative number solution that should be rejected if you're solving for real x

slim portal
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How about 3^(-999999999)?

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Is it = 0

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floral grail
#

what went wrong for me? the typed pic has the correct answer

lyric charm
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$\frac{1}{4\sqrt{y}} = \frac14 y^{-1/2}$ not $4y^{-1/2}$

grand pondBOT
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ann.in.a.teacup

floral grail
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ohh ok thx

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subtle peak
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How do I solve this?

midnight plankBOT
subtle peak
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Well I think I'm solving it correctly, I just can't get it into standard linear form

midnight plankBOT
#

@subtle peak Has your question been resolved?

sharp wave
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and your solution

subtle peak
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Certainly!

sharp wave
# subtle peak

after your first step why dont you divide by y^4/3 first then proceed

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i think you have made a calculation error afterward

sharp wave
subtle peak
sharp wave
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i dont think it matters, since you get rid of the dy/dx term straight away

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let me write and show you one sec

subtle peak
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It's the whole point of it

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See how I'm putting it into the bernoulli equation form to then find v?

sharp wave
subtle peak
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Ok, but how do you solve from there? It's not separable

sharp wave
# subtle peak

Oh, idk ive been taught to divide by y^n first then sub 1/y^n-1 as u or t

sharp wave
subtle peak
sharp wave
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Well, whatever works for you

subtle peak
sharp wave
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Your method is not wrong, im just not accustomed to it let me try though

subtle peak
sharp wave
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i think you should differentiate this with respect to x

subtle peak
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I see my mistake

sharp wave
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not the equation written below it

subtle peak
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No it's at where I plug it in

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Because I didn't divide by 3

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I multipled by 3*4

sharp wave
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oops

subtle peak
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Getting v^-12

sharp wave
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great you got your mistake

subtle peak
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Am I tripping or do we still not have the same answer though

subtle peak
sharp wave
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i divided by x

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the whole equation

subtle peak
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You're right, that's my second mistake

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I still have something different than you

sharp wave
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how have you differentiated?

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dy/dx = -3v^-4dv/dx

subtle peak
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Oh right. My math work is a festival of disappointments

sharp wave
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you can refer this if it seems easier to you

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i just feel its a lot less work

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again what you feel is best

subtle peak
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I'll stick with what the teacher taught us because I don't have time to afford learning a new technique

sharp wave
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sure!

subtle peak
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I will send this to myself and save it for later on though if I can

sharp wave
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great

subtle peak
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Dude, this semester has been brutal. It's been a year since I've touched calculus

sharp wave
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i hope you can carry on its like 12am for me and i really need to sleep

subtle peak
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Thank you for your help. I'll refer to your work

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Have a great night! Rest well

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!done

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subtle peak
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.close

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midnight plankBOT
sharp coral
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factoring is part of it, the other part is multiplying by the conjugate

gritty rune
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I see nothing wrong in your solution (its 12am so maybe im wrong too) but you can solve this using hopital it will be faster

lyric charm
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is somebody forcing you to do it that way??

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hrgh

gritty rune
lyric charm
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well ig you could pull a factorization of x-2 as x+2-4 and then as (sqrt(x+2)-2)(sqrt(x+2)+2) out of thin air

sharp coral
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you could factor [ x - 2 = (x+2) - 4 = (\sqrt{x+2} + 2)(\sqrt{x+2} - 2) ] but that's baroque enough that I don't think you could really think of it ahead of time

grand pondBOT
lyric charm
sharp coral
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i think that the method you used is fine for that prompt

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yes

midnight plankBOT
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@jolly roost Has your question been resolved?

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unique hornet
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I need help finding the area of the shaded region, i have no other angles or values that i can work with, can somebody help me continue?

shy marsh
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Calculate x using pythagoras

unique hornet
shy marsh
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like see them as one sector

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cuz they have same radius

unique hornet
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ohh so their angles combined are 90?

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unique hornet
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dense holly
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anyone good at circuits and physics

midnight plankBOT
dense holly
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?

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like kirchoffs law and stuff

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need help with this question

carmine sigil
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The two nodes immediately above and below the circled A are at the same potential. So R2 and R1 make a parallel circuit, and so do R3 and R4.

The current is divided through the two sets of resistors independently, so the current through A depends on how much they differ from each other.

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I would approach this problem in the following way:

  1. Find the effective resistances of R1 || R2 and R3 || R4
  2. Use those effective resistances to find the total current, and the voltage at A.
  3. Using the known voltage at A, find the current through each of the four resistors
  4. Using the known currents find how the currents differ, and how much needs to flow through A to make the circuit happy
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@dense holly

dense holly
dense holly
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to find U/V for the ammeter

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after i have the total resistance

carmine sigil
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You use Kirchoff's laws in several different ways

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But you can't use U/V for the ammeter, because there is no voltage change

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There is also no resistance

dense holly
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adding the resistances

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its gonna become a series circuit right?

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with Rp -- ammeter -- Rp smth like this?

carmine sigil
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R1 and R2 are in parallel

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Ah, yes

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Exactly

dense holly
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ok and i add both Resistances

carmine sigil
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Ignore the ammeter though, it's 0 resistance

dense holly
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i can get the total I

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1.5/R total

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then get the I individually for all the Rs?

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and just look around till i get a value?

carmine sigil
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Use voltage divider

dense holly
carmine sigil
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To get voltage at A

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V = IR for individual circuit elements as well

dense holly
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i dont understand the current flow tho

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is it from the bottom or up to the ammeter

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it depends on the sign of th e value?

carmine sigil
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You don't need to know immediately

dense holly
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aör

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alr

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ima give it a try

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see what. ican do

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thank you

carmine sigil
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Though with a little thinking qualitatively you can determine direction simply in this case

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We know that lower resistances get more current in parallel

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So we know more current goes through R1 than R2 and more current goes through R3 than R4

dense holly
dense holly
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more current from bottom

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leads to more current upwards

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through the ammeter node

carmine sigil
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Exactly, we can qualitatively determine that the ammeter is seeing current flowing upwards

dense holly
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i got total I as 0.0063amp

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6.3 mA

carmine sigil
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Then for the voltage divider, we have V_tot/R_tot = V_part/R_part as long as the part is in series with the rest of the circuit

dense holly
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sounds wrong

dense holly
carmine sigil
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This is equivalent to observing that the total current is constant

dense holly
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1/100 + 1/200 = 3/200 so Rp = 200/3

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did for both and in the end added as a series

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i then did 1.5/the value

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i got 0.0063 mA

carmine sigil
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That sounds reasonable

dense holly
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however

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I1 is 15mA

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I2 is 7.5mA

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or no wait

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forget that

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those were old values

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from previous arttempts

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how stupid can i be

carmine sigil
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Not stupid

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Just learning

dense holly
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actually

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that does make sense

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so look

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R1 for example is 100 Ohms

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i do 1.5/100 ohms

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that gives me 15mA

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thats more than the total?

carmine sigil
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Not quite!

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You haven't found the voltage at A

dense holly
carmine sigil
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The entire 1.5 volts isn't spent across that resistor

dense holly
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oh

carmine sigil
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It's less than 1.5

dense holly
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i forgot about that

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U = RI

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so

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uh

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do i use

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supplied voltage = total voltage drop?

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to figure that out

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or

carmine sigil
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V_tot/R_tot = V_part/R_part

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Using R1 || R2 as the part

dense holly
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i dont get it

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what is meant by a part

carmine sigil
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Using R1 and R2 in parallel as the part of the circuit that were examining to see the voltage drop across it

dense holly
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wait i found it i think

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for R2 and R1

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the parallel thingies

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isnt it just

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U = R * 0.0063

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cause the I total still applies there

carmine sigil
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Yes, that is another way to find this value

dense holly
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that gives

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0.42V

carmine sigil
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That seems reasonable

dense holly
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you said the ammeter has its own voltage right

carmine sigil
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So the voltage at A is what?

dense holly
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or

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am i wrong

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wait

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let me say smth

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the current is constant rn right?

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cause its technically a series circuit

carmine sigil
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The current though each pair is constant

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The current through the individuals can be different

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If we let I1 be the current through R1 and so on, then I1 + I2 = I3 + I4

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But none of I1 through I4 are necessarily equal

dense holly
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oh ok

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so what current do i use

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for R3+R4 ones

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not the same I?

carmine sigil
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You know the Voltage and you know the resistance, so you find the current

dense holly
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1.08/R?

carmine sigil
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0.42/R1 = I1

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Sorry

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Fixed

dense holly
carmine sigil
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Then 1.08/R3 = I3

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And so it goes

dense holly
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ok

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so

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4.2 mA for I1

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2.1 mA for I2

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3.6 mA for I3

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2.7 mA for I4

carmine sigil
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Those look reasonable

dense holly
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i total was 6.3 mA

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tho

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doesnt add up to that

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idk

carmine sigil
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It does actually

dense holly
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oh ur right

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cause its for I2 and I1

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only

carmine sigil
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I1 + I2 = I3 + I4 = I_tot

dense holly
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damn

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now

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i can use

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I total + I1 + I2 + I3 +I4 + Ia?

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or will it not work

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yeah nvm i sound dumb

carmine sigil
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Use the node laws, total current in = total current out

dense holly
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ok

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I total = I2 + I1

carmine sigil
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Focus on the node below A

dense holly
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ok

carmine sigil
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How much current is going in?

dense holly
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I1 = Ia + I4

carmine sigil
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Ok!

dense holly
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I1 - I4

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it gives

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11.25

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mA

carmine sigil
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Huh?

dense holly
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no wait

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im stupid

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i used the old values again

carmine sigil
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Not stupid

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Just learning

dense holly
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4.2 - 2.7

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1.5

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wow

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thats an A question for me

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difficult

carmine sigil
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A because amps? 😄

dense holly
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lmao

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thanks a lot

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you helped me i will remember this on the day i take that test

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means a lot

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gonna close this chat thank you again

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.close

midnight plankBOT
#
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carmine sigil
#

Yw! Have a good one

dense holly
#

.close

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.close

carmine sigil
#

It's closed

midnight plankBOT
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languid remnant
#

16/36 simplify to 16

midnight plankBOT
languid remnant
#

How to used squeeze theorem in this problem

subtle blaze
#

What does the squeeze theorem state?

languid remnant
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f(x)<=g(x)<=h(x) and limit equal at one point

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Then the limit of f(x) is also equal

subtle blaze
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So we need to find 2 functions f and h

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We are given a hint that -1 <= sinx <= 1

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But the function we want to “squeeze” is sinx/sqrtx

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(May be important but x is positive since we will take the limit)

languid remnant
#

are we using substitute ?

buoyant yoke
languid remnant
#

alright how to solve it?

buoyant yoke
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which functions did you find

languid remnant
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1/squareroot(x)

buoyant yoke
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is that f(x) or h(x)

languid remnant
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h(x)

buoyant yoke
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and then whats f(x)?

languid remnant
#

-1/squareroot(x)

subtle blaze
#

Perfect

#

At this point you just need to write it up nicely

languid remnant
#

oh ok

#

.close

midnight plankBOT
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radiant roost
#

how do we know that if r and s are coprime and both divide n, then rs divides n?

radiant roost
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hmm

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i just thought about it a little

midnight plankBOT
#

@radiant roost Has your question been resolved?

dawn dagger
radiant roost
#

i'm trying

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i haven't found anything worth posting

dawn dagger
#

what do you have so far

radiant roost
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i just know by bezout's identity we have rx+sy=1 for some x,y

dawn dagger
#

ok good

radiant roost
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we have rp=sq=n for some p,q

dawn dagger
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ok good

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now you could multiply the equation by n

radiant roost
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rxn+syn=n

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oh

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rxsq+syrp=n
rs(xq+yp)=n

dawn dagger
#

welcome in Algebra

radiant roost
#

thanks 🙏

#

.solved

midnight plankBOT
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orchid grove
midnight plankBOT
olive yew
#

could you explain the question

orchid grove
#

What do you mean?

#

I didn't understand it either

olive yew
#

same bro

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what does it mean in each subject there be necessary 1 bell

orchid grove
#

ABCDE

olive yew
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okay

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what we do here

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is first we give 1 particular bell to a class

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there is 6 bell and 5 class

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then we just give the rest of it to each class

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because each bell is distinct we can get 5!

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then try to solve it by yourself

midnight plankBOT
#

@orchid grove Has your question been resolved?

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ornate cliff
midnight plankBOT
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wintry plover
#

So im using a hyperbola to model a water bottle cap

kindred dagger
wintry plover
kindred dagger
#

Interesting

wintry plover
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I wanna rearrange this so itll equate to y=

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Which I did here but now im confused

kindred dagger
wintry plover
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If i should hse the positive or negative value

kindred dagger
#

Oh ig +/- works

wintry plover
#

Into the surface area of revolution

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Formula

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So idk if should use the positive or negative value of the B

kindred dagger
wintry plover
#

Or should I use a different program

wintry plover
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Of the function

kindred dagger
#

Are you trying to find the surface area or the volume

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Also is tihs supposed to be your bottle ?

wintry plover
#

I used the hyperbola equation

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But i limited the domain

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To only fit that part

midnight plankBOT
#

@wintry plover Has your question been resolved?

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orchid grove
midnight plankBOT
orchid grove
#

How can I do this?

#

I tried to look into 3d

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One lies on xy plane and other one over yz

blissful talon
#

This is a concept question. Do you understand what it means to be perpendicular to two vectors at once?

orchid grove
#

LI

blissful talon
#

true, but I mean visually. What does it look like?

orchid grove
#

If I join both vectors and made a line

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Then it would perpendicular to that line

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So it is 2?

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One point is upside

blissful talon
orchid grove
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Other one downside

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A line join both vectors

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And if I make perpendicular to its line joining

blissful talon
orchid grove
#

Actually i don't know its name

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But i can imagine

blissful talon
orchid grove
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a-b

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it is line equation

blissful talon
#

thinking about the line that joins the vectors is not the way to go

orchid grove
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So by fixed distance 5

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Only 2 possible

blissful talon
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a-b is not perpendicular to a or b

orchid grove
#

Nooo

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I am saying perpendicular to a-b

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which is 5

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Distance away

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One is upside

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Other one is downside

blissful talon
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there are infinitely many vectors perpendicular to a-b

orchid grove
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But 5

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Distance

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Soooo?((

blissful talon
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there are infinitely many vectors of length 5 that are perpendicular to a-b

orchid grove
#

Ohh

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My bad please guide me

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How can I solve it

blissful talon
#

when you have a vector in 3d, there are many perpendicular directions

#

think about a pen standing up on a table. Any pen lying on the table is perpendicular to it.

#

There's an entire plane of perpendicular

orchid grove
#

Yes sir

#

I can feel it

blissful talon
#

But if you must be perpendicular to two vectors, then you must be in both of those planes

orchid grove
#

So if i join these vectors

blissful talon
#

and those two planes intersect in a single line

orchid grove
#

And made a plane

#

So i can make infinite points?

blissful talon
#

Yes, one good way to approach this is to see that if you are perpendicular to a and b, then you are perpendicular to every combination of a and b, and thus to the entire plan that they span

#

So if you're perpendicular to a plane, now you either go to one side of it or the other

orchid grove
#

Yeah two plane

#

But here we have vectors

#

a×b?

blissful talon
#

a cross b is another approach to this question

orchid grove
#

Can you explain visually?

#

I did not understand what planes they are making

blissful talon
#

the set of vectors perpendicular to vector a is a plane

orchid grove
#

You meant yz plane and xy plane?

#

Which is y=0?

blissful talon
orchid grove
blissful talon
#

we're looking at vectors a and b. Each one lies in a line. It doesn't make sense to talk about what plane they line in because each one lies in infinitely many planes.

blissful talon
#

Do you understand the set of vectors perpendicular to a given vector?

orchid grove
#

Actually no

#

I can't imagine

#

😇😇😇

orchid grove
#

I will be back

#

Yes this way i made those vectors where they lie

#

a vector lies in xy plane

#

B lies in yz

blissful talon
#

those are technically true, but totally useless

#

(0,1,0) also lies in xy plane and in yz plane

orchid grove
#

These planes they lie

blissful talon
#

choosing a single plane that your given vector lies in is not useful

orchid grove
#

Can you make that plane in desmos 3d?

#

So that i can understand better because it is language barrier

blissful talon
#

You keep saying that a vector lies in a plane, but that's useless.

orchid grove
#

Okay

blissful talon
#

The vector (1,1,0) lies in infinitely many planes.

orchid grove
#

Okay sooo

#

What should I do quickly

#

This is the plane at the start i was saying you which joins both of them

#

And perpendicular

#

5

#

Not exaclty same plane but it will look like this

blissful talon
#

that plane contains infinitely many vectors of length 5

orchid grove
#

a-b=(1,0,-1)

orchid grove
blissful talon
#

no, because this plane that you wrote down doesn't come from anywhere

#

Try to name 3 vectors in different directions that are perpendicular to (1,1,0)

#

Alternatively, you could try to find a single plane that contains both a and b

midnight plankBOT
#

@orchid grove Has your question been resolved?

orchid grove
blissful talon
#

state

#

Say what the vectors are

#

Is (1,2,3) perpendicular to (1,1,0)?

orchid grove
#

I need to check it with determinant

blissful talon
#

How does that work?

orchid grove
#

Ohh you asking me two

#

I will cross product

#

Or dot product

blissful talon
#

Those two are very different

#

I think you are missing a lot of information here.

orchid grove
#

I am confused actually

blissful talon
#

You should look up what not just what dot and cross product formulas are, but what they mean conceptually

orchid grove
#

If cross product is 1

#

I read about and try to watch in 3D about dot product in cross product so in doubt product if we have prependicular then what's the time will be zero so if don't product is zero then we can asume that those two vectors are perpendicular

#

@blissful talon

#

(1+2+0)=3

#

Not perpendicular

#

I can't use cross product for perpendicular year if two vectors are given

blissful talon
#

Now find 5 different vectors that are perpendicular to (1,1,0), and graph them all on desmos at the same time

orchid grove
#

I can't graph them

#

Actually

orchid grove
#

The question is already too time

blissful talon
#

Now find 5 different vectors that are perpendicular to (1,1,0), and graph them all on paper at the same time

orchid grove
#

(-1,1,2),(-2,2,5)(4,-4,6)

#

@blissful talon

#

I can make many

#

Dot product is zero

#

.close

midnight plankBOT
#
Channel closed

Closed by @orchid grove

Use .reopen if this was a mistake.

orchid grove
#

.reopen

midnight plankBOT
#

orchid grove
#

Cross product of two vectors gives a vector that is perpendicular to both of vector and it can be two types one is upset one is down side

#

@blissful talon

#

And the length is 5 so it can be two option

#

That's it and it was very easy and now I am closing it

#

.close

midnight plankBOT
#
Channel closed

Closed by @orchid grove

Use .reopen if this was a mistake.

blissful talon
#

that tells you that it's AT LEAST 2, but you don't know that it isn't more. 🤷

orchid grove
#

I am sorry but i am not understanding your way of explaining

#

Thanks for helping

blissful talon
#

Fair enough. Good luck.

midnight plankBOT
#
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woven lion
#

can someone help for this? I am really confused, dont know where to begin

white gate
woven lion
#

How do I use the results? Why are we adding?

white gate
#

we want to only obtain e^x cos(x)

woven lion
white gate
#

$\frac{d}{dx}\left( e^x\sin x+e^x\cos x \right)=2e^x\cos x$

grand pondBOT
#

TargetVN

white gate
#

it's just (1) + (2)

woven lion
#

?

#

idk

white gate
#

i mean you just add those 2 equations together, then integrate both sides

#

that's it

woven lion
white gate
#

it vanishes

#

the sum of those is 0

woven lion
#

ah

#

so yea 2e^xcosx

#

then I integrate 2e^x cosx?

white gate
#

more specifically, you integrate both sides

woven lion
#

wdym by both sides?

white gate
#

at the LHS, d/dx and integral sign will vanish

white gate
woven lion
white gate
#

No

#

like this

#

and i do mean literally

#

straight up integrate both sides

woven lion
#

ah

#

where did you get 1/2 from?

white gate
#

divide both sides by 2

woven lion
#

ah

white gate
#

the coefficient doesnt affect differentiation and integration

woven lion
white gate
#

i mean, the initial coefficient

woven lion
#

ah

white gate
#

the derivative of x^3 just add more coefficient, but the 2 remains

woven lion
#

i see

woven lion
white gate
#

ofc not

woven lion
#

had a feeling

white gate
#

d/dx and integral sign cancels out, then u have the answer

woven lion
white gate
#

cancel out as normal

woven lion
woven lion
white gate
#

2 d/dx of separate functions = d/dx 2 functions

#

$\frac{d }{dx}\left( f+g \right)=\frac{d }{dx}f+\frac{d }{dx}g$

grand pondBOT
#

TargetVN

midnight plankBOT
#

@woven lion Has your question been resolved?

#
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#
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prime garden
#

Find a point X inside a triangle ABC such that area(AXB) : area(BXC) : area(CXA) = k : l : m
where k, l and m are given constants.

chrome vessel
last slate
#

best to draw this out

#

(if you haven't already that is)

lyric charm
#

let him share what he's got so far with us, people

prime garden
#

I ask: Is it allowed to divide a line segment in a desired ratio?

chrome vessel
prime garden
#

Sol.:
Drop the perpendicular from A onto BC.
area(AXB) = kx, area(BXC) = lx and area(CXA) = mx.
area(ABC) = area(AXB) + area(BXC) + area(CXA) = x(l+k+m)
area(AXB) : area(ABC) = kx:[x(l+m+k)] = k:(k+l+m)
Similarly, area(BXC) : area(ABC) = l:(l+m+k).
area(BXC) = XE * BC/2
area(ABC) = AE * BC/2
area(BXC) : area(ABC) = XE:AE = l:(l+m+k).
So find a point X on AE such that AE:XE = (l+m+k):l
Draw a line parallel to BC such that it goes through X. All the triangles that have the base BC and an area equal to (area(ABC) * l)/(l+m+k) will have the third vertex on the line GF (since triangles having an area equal to one another and on the same base lie between the same parallel lines).
We can do the same for the other sides. The point of intersection of the parallel lines will the actual 'X'.
Is this correct?

#

Shouldn't I also have to prove that the three parallel lines formed will be concurrent?

chrome vessel
prime garden
#

Yes.

chrome vessel
#

which might note be the case

prime garden
chrome vessel
chrome vessel
#

but two parallel lines are sufficient: Let them intersect at X, and show that the area of the third shape has the desired area

prime garden
#

yup

#

We can force the third line to intersect at the same point

#

Thank you, is everything else correct?

chrome vessel
# prime garden Thank you, is everything else correct?

the line "All the triangles that have the base BC and an area equal to (area(ABC) * l)/(l+m+k) will have the third vertex on the line GF (since triangles having an area equal to one another and on the same base lie between the same parallel lines)." needs some modification

#

third point lies on parallel line -> same area, but not the other way around.

#

you'd have to show (fixed area+ third point lies inside the triangle -> third point lies on parallel line).

#

but the modification shouldn't be too difficult

prime garden
#

<@&268886789983436800>

chrome vessel
lyric charm
# prime garden I ask: Is it allowed to divide a line segment in a desired ratio?

no, you don't have the specialized permit for it. you need to submit a request to your local math board and attach exactly 4 forms of identification (5 or more = rejection) each one valid for at least 8 months beyond the date of application, with the form filled out in blue ink if it's an even day or black if it's an odd day (wrong color = rejection), then wait 7 to 12 business days to collect the physical copy of your permit. it is valid for exactly 4 months and 11 days.

(massive joke)

midnight plankBOT
#

@prime garden Has your question been resolved?

#
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midnight plankBOT
#
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After 15 minutes, feel free to ping <@&286206848099549185>.
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graceful ferry
#

There's a theorem that says if f' is bounded then f is uniformly continuois,
Can I say if f' is not bounded then f is not uniformly continuous ?

dawn dagger
dreamy lichen
#

sqrt(x) on the interval (0, inf) could be a counterexample

visual tiger
#

sqrt(x)

graceful ferry
#

Contraposition?

visual tiger
graceful ferry
#

Ok nvm sqrt(x) is counterexmaple yea

visual tiger
#

even worse counterexample!

graceful ferry
visual tiger
graceful ferry
#

Ohh

dreamy lichen
visual tiger
#

yeah, also even worse counterexample:

#

weierstrass function on [-1,1]

#

uniformly continuous

#

but derivative doesn't even exist

#

anywhere

graceful ferry
#

Huh haven't heard of his function yet

dreamy lichen
#

It's basically a fractal-ish function which is continuous everywhere but differentiable nowhere

graceful ferry
#

There it is

unique juniper
graceful ferry
#

Why does it look like that help😭

unique juniper
#

it's made to be continouous but indifferentiable

graceful ferry
#

It reminds me of a video I've watched long ago ugh

dreamy lichen
graceful ferry
#

That's interesting !

#

I can't find the video I got a flashback of :(

#

.close

midnight plankBOT
#
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midnight plankBOT
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prime garden
#

Prove that 2p^2 is never a perfect square where p is an integer.

midnight plankBOT
#
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
prime garden
#

2p^2 = j^2
j = root(2) * p
p is an integer. This implies j is irrational. So 2p^2 is not the square of an integer, making it a non perfect-square.
Is this proof correct? Lol
p is an integer

lyric charm
#

what is p?

fresh sparrow
#

assuming you already know that root(2) is irrational, yes

lyric charm
#

ok the fact that p ∈ Z should have been added to the question itself not to your proof

#

but other than that,

  • is the irrationality of sqrt(2) known already?
  • if it is, can you explain why sqrt(2)*p is always irrational?
#

also you want to exclude p=0, yes?

#

@prime garden

prime garden
#

yes

#

I should stop labelling everything a 'proof'.

#

I can prove those two points.

#

thank oui

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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still tartan
midnight plankBOT
still tartan
#

I need help with that

lyric charm
still tartan
#

I read the previous examples and even watched the video under it...I still couldn't get it

lyric charm
#

ok so notice how all the lines here go through one corner of one triangle and one corner of another

#

ok well actually no the ones in A and E go through two corners of the smaller one

#

but that actually lets you reject them automatically bc if they really were passing through the center of enlargement they'd also go through 2 corners on the big one

#

and they don't

#

do you understand this point? (i am not done yet)

still tartan
#

Hang on

lyric charm
#

oh actually no i have to go now so im just gonna drop the rest of my explanation

#

for the other lines here you want to make sure they go through a pair of CORRESPONDING corners of the two triangles.

#

like for example C won't do because it goes through the right angle in the big triangle but not through the right angle in the small one

still tartan
#

So it's B,D,F

#

I got it, thanks

midnight plankBOT
#

@still tartan Has your question been resolved?

#
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lyric scroll
#

3x-4y+2z=5
2x-y-z=0
4x-2y-2z=12

midnight plankBOT
lyric scroll
#

yo so

#

i did III * 2

#

and did I-III‘

#

(III*2 is III‘)

#

so then

#

we have IV = -5x+6z= -19

#

and then we do the II * 4

#

and then we do I-II'

#

then we have -5x-2z=5

#

but now

#

z=-3

#

but the solution says no solutions exisz

#

what did i do wrong?

alpine gyro
#

If you multiply the second equation by 2, you’ll get something identical on lhs to one of your equations.

lyric scroll
#

lhs?

drifting birch
#

left hand side

lyric scroll
#

but what did i do wrong

#

i eliminated a variable

#

like always

drifting birch
#

Can you show what you actually did, reading this is hard to understand

#

😢

lyric scroll
#

my handwritins is gruesome

#

and i didnt properly write everything

#

ok but wait

#

let me rewrite it

#

wait

#

why?

#

ok wait

#

wait it should be correct tho

drifting birch
lyric scroll
#

z?

drifting birch
#

2z-(-4z)

lyric scroll
#

-2-(-4)

#

thats -2 right

drifting birch
#

yeah mb

drifting birch
lyric scroll
#

yo

#

wtf

#

😭

drifting birch
#

-2+4

#

🙏🏻

lyric scroll
#

man i keep doing stupid mistakes

drifting birch
#

oh wait why did he write -2-(-4)

#

I thought he was right lmao

lyric scroll
#

wait no

#

its 2-4

#

3x-4y+2z=5
-8x-(-4y)-4z = 0

#

wait

#

im so fucking confused

grand pondBOT
#

lin.fei ‧₊˚❀༉‧₊˚.

drifting birch
#

-(8x-4y-4z)

lyric scroll
#

what?

#

wdym

#

oj

#

yeah

#

why minus 4 tho

#

i did times plus 4

#

wait listen

#

OH my god

#

its -z not +z

#

YO

#

FUCK YEAH

#

-5x+6z = 0

#

and -5x +6z = -19

#

so now i do -5x+6z = 0 minus -5x+6z = 0

#

0 is not -19

#

so no solution

#

okay 1 more

#

wait here

#

so u mean eliminate z

#

first?

#

oh

#

i see

#

the II and III

#

ok wait dont go yo

#

so

#

4x-5y=-4
5x+3y=32

#

i did I times 5

#

and II times 4

#

and did I'-II'

#

but idk also doesnt make sense

#

yo

fallow scarab
#

show the result of the difference

lyric scroll
#

its 37x = 128

fallow scarab
#

what eqn is I and what eqn is II

lyric scroll
#

oh

#

okay

#

20x-25y=-20
20x+12y=128

fallow scarab
#

you just subtract them, no differencing needed

#

20x-20x = 0

lyric scroll
#

wait wdym

lyric scroll
fallow scarab
#

yes

lyric scroll
#

yes so then we have

#

yeah but i think

#

it doesnt make senes

fallow scarab
#

why

lyric scroll
#

cuz on wolfram it says no solution

fallow scarab
#

show

lyric scroll
#

ok wait

#

oh

#

its 4 and 4

#

ok mb

midnight plankBOT
#

@lyric scroll Has your question been resolved?

#
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grand pondBOT
#

waffle

kindred dagger
#

i think you messed up

#

can you show your work

kindred dagger
#

but you said positive 1

grand pondBOT
#

waffle

#

waffle

#

waffle

kindred dagger
kindred dagger
#

,w arcsin(cos(x)) = pi/2 - arccos(cos(x))

kindred dagger
#

✅ @earnest forge

midnight plankBOT
#
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kindred dagger
#

lol

midnight plankBOT
#
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serene rose
#

How do I find X

midnight plankBOT
drifting birch
#

Did you not ask this an hour ago

#

😭

#

They are the same angle

drifting birch
#

You can find it from supplementary angles, 180-94

serene rose
# drifting birch

I still don’t get how their supplementary and how to write the equation

drifting birch
#

since they are the same you equate

#

180-94=13x-5

serene rose
#

Ok

#

.close

midnight plankBOT
#
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midnight plankBOT
#
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vocal briar
midnight plankBOT
vocal briar
#

i was told to show more reflection in my math lab

#

and one of the things I was talking about is how i had a leaf and assumed that it was flat and had no z-axis protrusions

#

would this be considered a non-euclidean object in that regard and why would it be wise to assume that the leaf is flat?

#

i'm assuming that the work of implementing multi-variable calculus and non-euclidean geometry concepts would overcomplicate the problem for a minor change in surface area

#

but how could i speak on it

humble steeple
#

i mean ideally u shouldve flattened out the leaf urself but if u didnt, u dont need to talk about non euclidian geometry at all. u can just say that dealing with multiple variables is futile for negligible changes in results

vocal briar
#

right but i need more thinking about the problems and a proper justification for the reasons

#

if i js say that the change in SA would be negligible regardless or that I didn't have the technology to take a 3D scan

#

like I js want to be able to speak on more if I can

#

since js saying that i didn't want to cuz i couldn't or that its not worth it is not really that strong of a justification in my opinion

#

another assumption i've made is that this was a perfect ellipsoid

#

is there something that I can talk about here as to why? The real reason I did this was because if I assumed it was a circle then I would literally plug it into 4pir^2 and get the surface area but assuming it was an ellipse allowed for me to use calc

humble steeple
#

what is ur research question

vocal briar
#

To what extent can calculus be applied to calculate the surface area of leaves?

humble steeple
vocal briar
#

that is a string-of-pearls leaf

humble steeple
#

i see

vocal briar
#

which is unique in that it appears spherical

humble steeple
#

so u r taking different types of leaves?

vocal briar
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yeah and finding the surface area using different methods

humble steeple
vocal briar
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so with the flat banana leaf i took polynomial interpolation and matrices to explain it, with this i explaiend the riemans sum and disk integration and with my last example it was more logic based since it had overlapping domains of piecewise functions

humble steeple
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perhaps there r values on the internet

vocal briar
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but there is certain assumptions I have to make for the hs level

humble steeple
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is this IB?

vocal briar
vocal briar
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math ia

humble steeple
humble steeple
vocal briar
humble steeple
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or sl

vocal briar
humble steeple
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u should be fine by justifying that the topic gets too difficult with the inclusion of more variables for example

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u arent required too much rigor at aa sl

vocal briar
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yeah so basically my teacher said to include more student voice and reflection of the process

vocal briar
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ok

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what about for the second exmaple?

humble steeple
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reflection could mean some other methods that could be explored

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like ur ellipsoid leaf

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u could talk about a simpler way being assuming its spherical

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does this leaf more accurately resemble an ellipsoid btw?

vocal briar
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yeah

humble steeple
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u can justify it through that

vocal briar
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ok fair enough

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also

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since i alr asked for the first wto

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can you explain for the english ivy example i have

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basically, I was doing this the night it was due so after calculating it for half the leaf I sadi we can just assume bilateral symetry so i wouldn't have to do the whole process for the bottom half

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but is there a justification i can say as to why

humble steeple
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thats a bad assumption

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u should probably calculate it properly

vocal briar
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okay fair enough

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if I did then what would i talk about then

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for reflection criterion

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i wouldn't necessarily be assuming anything in that example

humble steeple
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u can talk about ur previous methods used

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so u can talk about how u wanted to assume bilateral symmetry but realized it would cause a large margin of error

vocal briar
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if i overlay the shaded area on the bottom half as an image and show that this wouldn't be the most accurate assumption then would that be a really good point in terms of PE and reflection?

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like are diagrams better for this stuff

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or would it not matter

humble steeple
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yes diagrams r the best

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they boost personal engagement

vocal briar
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ok W

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i have a bunch

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also

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can you see if there is any topics in particular I should be touching on here

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I was talking about rieman's sum and after deriving the formula, i said that this just appears in the arc length formula

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but I didn't really explain how, is there certain key concepts I should talk about if anything comes to mind?

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I feel like this might increase the reflection as well

humble steeple
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first of, replace the delta by d in ur arclength derivation

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its important to emphasize that its a differential, not a discrete change

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oh u used it in a discrete way

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did u evaluate the integral at the end?

vocal briar
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yeah this is what I've said

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I feel like I can expand on the first sentence maybe?

humble steeple
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u could actually compute the integral using numerical methods

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it will boost engagement

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u can use the riemann sums but with n = 10^8 for example

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and use a code that iterates those many times (if u have programming background, or just ask gpt to code a riemann sum calculator)

midnight plankBOT
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@vocal briar Has your question been resolved?

midnight plankBOT
#
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midnight plankBOT
#
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viral citrus
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This question i need second opinion on the answer

viral citrus
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The black and red on the top left is what someone i know and their tutor did

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And the work i did was the blue on the bottom right

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The part i was most skeptical about for my answer was the formula for projected length

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The answer the tutor of my friend gave didnt really make sense to me given that the surface area of the ellipse would decrease as theta increases

viral citrus
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But SA should increase as the cup tilts

west iron
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yes, pi*r^2*cos(theta) isn't right for that reason

viral citrus
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Ok im glad im not just missing something there

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I dont think the math i did was wrong but the only thing that really bothers me is the formula for the projected length

west iron
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the height goes from h to hcos(theta)

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the cross sectional area needs to increase to compensate

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the new area should be pi*r^2/cos(theta)

viral citrus
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Ok perfect so i got that right

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Now i have a concern and it may be that the question just doesnt specify what happens in the situation but…

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At some point shouldnt the water not reach the middle of the bottle when tilting? Its hard to explain with words but lets say there is a water bottle with some water in it. As you tilt the water doesnt reach the radius/center of the bottle which then means the other axis that used to be constant, now isnt.

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Sorry if i explained it poorly.

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Maybe i can draw diagrams to explain better

west iron
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ye idk what u mean

midnight plankBOT
#

@viral citrus Has your question been resolved?

viral citrus
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God my diagram made it more confusing

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Honestly i seriously doubt that they’ll consider this since it would make the question nearly unsolvable with the info provided

viral citrus
midnight plankBOT
#
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midnight plankBOT
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tired ferry
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Why is the relation clearly reflexive?

midnight plankBOT
tired ferry
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just by definition of partition?

dawn dagger
tired ferry
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Ok, so its like by definition of the partition

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The reason im asking because its suposed to be a proof proving that partitions imply equivilance relations

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so idk if thats the right way to look at it because it should be something we are trying to prove

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if that makes sense

radiant roost
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he's right

tired ferry
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whos?

radiant roost
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i agree with it

tired ferry
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Ok

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my question is

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is that not something we are trying to prove?

radiant roost
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they defined a relation, by saying that a is related to b if there exists X_i with a,b both in X_i