You have just entered room "calcdchat."
abbymath92: hi
chejam4 has entered the room.
abbymath92: how's it going?
chejam4: good
liufan04 has entered the room.
TheNecropolist: hi
TheNecropolist: I'm going to fail the math test :-(
abbymath92: I don't think so
TheNecropolist: ms. brown, can you do 17, 18, 19 from larsons?
w0n0ne has entered the room.
w0n0ne: hello
abbymath92: hi
w0n0ne: is there a question on the floor?
abbymath92: Michael: Pick one for me to do first...we'll see how it goes
w0n0ne: ok
TheNecropolist: okay, my problem with 17, i still can't take those derivatives!
abbymath92: I just logged in...I need to get my stuff...brb
abbymath92: I'll get the whiteboard set up
TheNecropolist: okay
abbymath92: but it will take a couple minutes
TheNecropolist: okay i'm playing a game anyways
loveEstela 222 has entered the room.
loveEstela 222: hi
abbymath92: does anyone else have a question I can answer while my tablet boots?
chejam4: i do i think
HeadISBAgent: yea
HeadISBAgent: just quick question
chejam4: for stokes theorum, if the curl ends up having three variables, do we just substitute one of them with the equation of g(x,y) or something?
HeadISBAgent: and also, if it gives like the three vertices to a triangle, do we get the gradient by finding the eqn of the plane?
abbymath92: James: yes
TheNecropolist: alan : y es
TheNecropolist: alan: i did that today!!!
TheNecropolist: that's 11 right?
abbymath92: you would have to get it into the variables you use in dA
TheNecropolist: that's the only problem I know how to do, as of now
chejam4: ok
HeadISBAgent: ok thanx
abbymath92: Michael: you're having trouble with the curl on 17?
TheNecropolist: yes
TheNecropolist: for the z part
abbymath92: the derivative of arctan x is 1/(1+x^2)
TheNecropolist: yeah I know that, I looked it up
loveEstela 222 has left the room.
TheNecropolist: but I'm having problems with chain rule
abbymath92: so if you want the derivative of arctan (x/y) with respect to x, then you would get
abbymath92: 1/(1+x^2) * 1/y
abbymath92: oops!!
abbymath92: that's not right
abbymath92: I mean....
loveEstela 222 has entered the room.
abbymath92: 1/(1 + (x/y)^2) * (1/y)
TheNecropolist: okay
thisisomario has entered the room.
thisisomario: weird, I thought I was here a second ago and it was empty..
abbymath92: the derivative of ln x is 1/x
abbymath92: (maybe you were in Calc C by mistake)
abbymath92: so then the derivative of -ln(sqrt(x^2 + y^2)) would be
abbymath92: derivative with respect to y:
TheNecropolist: oh, I dont' think I remember learning this
abbymath92: -1/sqrt(x^2 + y^2) * 1/2 (x^2 + y^2)^(-1/2) * 2y
abbymath92: it's the chain rule
abbymath92: I know Mr. Williams taught it to you :-)
abbymath92: well, I guess, whether you "learned" it is a different question ;-)
TheNecropolist: maybe I was sick
chejam4: sick of learning?
abbymath92: it's not a one day topic
TheNecropolist: oh, well I'm a slow learner
thisisomario: lol
chejam4: on the integral signs do we have to write the C's S's and E's?
TheNecropolist: yeah, like the double integral over S
TheNecropolist: that's confusing
chejam4: and what does E stand for?
abbymath92: you should write something under the integral sign
loveEstela 222: isn't E supposed to be a solid?
abbymath92: that indicates the domain over which you are integrating
TheNecropolist: can it be anything?
loveEstela 222: no
abbymath92: it's a placeholder until you fill in the acutal limits
abbymath92: well, it's not always exactly the same from book to book, but here's what I use:
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abbymath92: Double Integral over R of the function dA
abbymath92: that's when the dA is rectangular or polar
abbymath92: Double Integral over "D" of the function when dA is dudv as in parametric surfaces
abbymath92: That's the Larson notation
abbymath92: the Stewart book (your book) uses "R" for rectangular shaped regions and "D" for any other 2-dimensional domain
abbymath92: I don't like that because so what if the region is rectangular....it's still a double integral dA
TheNecropolist: can I use a :-) for the domain if it helps to boost my self-esteem?
loveEstela 222: .....
abbymath92: Triple Integrals: I use Q or E. Larson uses Q and Stewart uses E.
chejam4: Does it stand for anything?
abbymath92: Q is close to R and E is close to D, so that kind of matches what they prefer for double integrals.
abbymath92: I usually write E because it makes me think of three (triple integral), but sometimes I write Q out of old habit
thisisomario: Ms. Brown - could you help me with a problem from the Larson handout?
abbymath92: Line Integrals: Always over C for "curve." Sometimes the C is dropped when the "circle integral" notation is used.
abbymath92: Shoeb: Yeah...hang on
thisisomario: k hehe
abbymath92: (Do you know the one I mean? The integral sign with the little circle.) I don't use that because line integrals are line integrals whether they are closed curves or not
abbymath92: besides, it looks like some freaky other kind of integration.
thisisomario: lol, but it saves you having to determine whether the C is closed :P
abbymath92: Surface Integrals dS or dS are always over S for surface
abbymath92: (but if you're the one developing the problem in some application or something you have to figure that out anyway.)
thisisomario: ok fine, you win hehe
w0n0ne: can someone do 16.7 13
abbymath92: Once the dS or dS becomes "dA" then I change the letter to R (or D) to go with the dA because now the surface integral has been reduced to a double integral that we can acutally calculate
abbymath92: does this help?
TheNecropolist: do we have to put a vector thing on dS?
abbymath92: if it's a scalar problem, you better not put one there.
thisisomario: if it is a vector, then yes..
abbymath92: if it is a vector problem, you must have one there
TheNecropolist: how do I tell
abbymath92: Shoeb: Which one on Larson?
thisisomario: 11, with the triangle on it
thisisomario: I don't understand how to use the information from the triangle as "S"
abbymath92: Matthew: for 16.7 #13, I put a hint on the assignment sheet. Finding delG for this is similar to the one on the last page of the 16.7 class notes that I passed out to you.
abbymath92: three points define a . . . . ?
loveEstela 222: plane
thisisomario: plane.. ahh.. that works
loveEstela 222: right?
abbymath92: yup
thisisomario: hmm, ok, so we could form an equation for the plane, but then that wouldn't define the area we integrate over properly..
thisisomario: or am I missing something heh
abbymath92: you have to decide which coordinate plane you want to consider to be the "domain" for the surface
abbymath92: pick what makes the most sense by looking at (1) the integrand and (2) the equation of the surface
Dragonflare211 has entered the room.
abbymath92: hi
Dragonflare211: hi ms brown
TheNecropolist: chris what hw are you on
thisisomario: ok.. so, in this case, it doesn't matter a huge deal does it?
thisisomario: lol
Dragonflare211: hw number 1
loveEstela 222: of course
Dragonflare211: really blows cause i did it before
Dragonflare211: and i lost it
Dragonflare211: ask shoeb
thisisomario: yes, think everyone knows that by now..
abbymath92: haha
Dragonflare211: hey bad ms brown
Dragonflare211: u can't laugh at me!
abbymath92: at least it's the easiest one to redo
Dragonflare211: grrrrr
Dragonflare211: blah
thisisomario: yeh, that;s true chris..
abbymath92: and you have until Monday to redo it
Dragonflare211: heheheheh
TheNecropolist: chris, we're at the same place
Dragonflare211: don't u mean tuesday :)
chejam4: tuesday during lunch
TheNecropolist: except did 5 assignments on sunday
Dragonflare211: lol michael i already finished 2 of them
abbymath92: yeah..whatever
TheNecropolist: I did 5 assignments on sunday
Dragonflare211: lol
liufan04: michael, I don't think you did 5
Dragonflare211: ok i'll do all the rest on monday then
Dragonflare211: need to study
TheNecropolist: how many did I do?
abbymath92: Matthew: did you get #13?
liufan04: 3
TheNecropolist: it was at least 4
TheNecropolist: and i think we started on 5
liufan04: no, 3
Dragonflare211: .... doubtful
TheNecropolist: no, i just checked
liufan04: if you did 5 on Sunday, you were done by yesterday
Dragonflare211: i still trust fan more than u
liufan04: thax Chris
liufan04: I am flattered
Dragonflare211: lol\
Dragonflare211: u should be!
Dragonflare211: i mean if i didn't that owuld be the end of the world
TheNecropolist: oh well, I don't value chris's opinion
abbymath92: Is there a question posted that I haven't answered yet?
Dragonflare211: yesh
TheNecropolist: are there t/f questions again?
Dragonflare211: hw 1 problem all :)
Dragonflare211: then hw 2
hwangang1337: For the Vector Line integral , if it is Conswervative we can use Fundamental theorm of line integral right ?To find conservative Do use curl F = 0
thisisomario: Ms. Brown - I still don't quite understand how to use the plane as the surface--after picking a variable do I try and set bounds that "cut" the triangle out of the plane?
liufan04: the projection
liufan04: the projection onto a coordinate plane will give you the boundaries
abbymath92: Alex: yes, yes
Gottmilk423: i have a question on the last homework
abbymath92: unless it's 2D, then use delQ/delx = delP/dely ?
abbymath92: Shoeb: To find the region in, say, the xy-plane, project it onto the xy-plane
abbymath92: it would just be the triangle formed by making the z-coordinates 0
thisisomario: the projection of a plane though -- i don't understand how it would get me the boundaries... argh, I think I am confusing myself lol
abbymath92: thanks, fan....didn't see your response
Gottmilk423: larson #11
abbymath92: Jordan: what's your
Gottmilk423: has it been done yet?
liufan04: 11 is the triangle one, right?
Gottmilk423: yeah
Gottmilk423: it's the triangle that's messing me up
TheNecropolist: i know how to do that one!
abbymath92: I think that's the same one Shoeb and Fan are discussing
thisisomario: yeh same one.
Gottmilk423: ok
abbymath92: So the poitns are (0,0,0), (0,2,0) and (1,1,1)
TheNecropolist: it's easier to project it onto the xy plane
abbymath92: let's use the xy-plane as the domain over which the surface is for the integral
thisisomario: k
abbymath92: so in teh xy-plane, we have the triangle with vertices (0,0), (0,2), (1,1)
abbymath92: use taht to find the limits for the double integral
abbymath92: you'll need to find teh equaiton of the line connecting some of the points though
Gottmilk423: so y goes from x to 2-x, and x goes from 0 to 1?
abbymath92: Doing it in my head....wouldn't y go from x to 2?
abbymath92: oh! never mind....
abbymath92: you're right
Gottmilk423: so the only thing left is finding the gradient of G to set up the integral, right?
TheNecropolist: oh i know how to do that part!
thisisomario: how the heck did you guys figure that out so fast.. I was busy drawing my triangle and you had answers lol
loveEstela 222: so y=g(x) and G(x) = y-g(x)?
TheNecropolist: ummm no
TheNecropolist: G =z-x
TheNecropolist: backwards delta G = <-1, 0, 1>
Gottmilk423: so gradient of G is <-1,0,1>?
Gottmilk423: yeah
TheNecropolist: yeah
loveEstela 222: what?
thisisomario: wait, why is G = z - x?
TheNecropolist: to find the gradient
TheNecropolist: you need to have two vectors
TheNecropolist: so you make two vectors from your three points
thisisomario: and corss them?
thisisomario: *cross
thisisomario: to find the plane?
TheNecropolist: the easiest are <1,1,1,> and <0,2,0>
TheNecropolist: yeah
TheNecropolist: and you cross it
thisisomario: ah... and then use that to find g..
TheNecropolist: and then you make the plane eqn with a(x-xo) + b(y-yo)... etc
TheNecropolist: yeah
thisisomario: oh that makes sense now..
thisisomario: thanks guys :-)
Gottmilk423: the integrand is 1?
TheNecropolist: yeah
Gottmilk423: weird
abbymath92: the integrand is whatever you are asked to integrate in the original problem
abbymath92: n'er mind.... is the "1" what you get after the dot product?
Gottmilk423: yeah
Gottmilk423: all that work for such a simple integral...
TheNecropolist: yeah, that's math
TheNecropolist: and life too
thisisomario: lol
oddperson12 has entered the room.
TheNecropolist: Rooney!
oddperson12: hi
IssacPao 9 has entered the room.
IssacPao 9: how come no ones talking?
Gottmilk423: in the triangle one, how can we just use the projection?
TheNecropolist: cause fan said so :-\
liufan04: .....
Gottmilk423: i mean
Gottmilk423: it works
liufan04: the plane took care of the z part
Gottmilk423: what plane?
liufan04: so the projection takes care of the rest
TheNecropolist: the plane z-x
liufan04: the plane you made with two vectors
HeadISBAgent: the surface is accounted for in the integral
Gottmilk423: right
Gottmilk423: okay
abbymath92: sounds like you guys got it :-)
thisisomario: one hell of a problem though lol
abbymath92: when you do a surface integral, the surface information is caputred in two parts
abbymath92: (1) the del G dA when you convert the dS (or dS)
abbymath92: and (2) the domain for the dA over which you are integrating
abbymath92: does that make sense?
abbymath92: it's a good one...not too complicated to do if you understand the steps
TheNecropolist: do we have to review the different shapes?
loveEstela 222: hi sorry to be the slow one
abbymath92: shapes?
TheNecropolist: ellipsoid, elliptic cone, etc.
loveEstela 222: but how did the integrand come to be 1?
TheNecropolist: after you dot them you get 3-2
abbymath92: why would you need to review that? you should know it by now ;-)
TheNecropolist: it's not as exciting as the periodic table, I didn't bother to take the time to memorize them
loveEstela 222: you're dotting <2y, 3z,x> with <-1,0,1>?
TheNecropolist: did you do the curl?
TheNecropolist: the curl result should be <-3,-1,-2>
loveEstela 222: curl? ooooh
TheNecropolist: yeah you forgot the curl
TheNecropolist: stoke theorem is curl dot backwards delta G dA
HeadISBAgent: off-topic but does anyone know brian alfred's SN? i need to ask him something
TheNecropolist: calamite47
HeadISBAgent: thanx
TheNecropolist: not online though
HeadISBAgent: bleh ok :P
TheNecropolist: it's alford btw
HeadISBAgent: whoops ><
hwangang1337: How to find the function f such that Gradient f = vector F function
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TheNecropolist: are you working on a specific problem?
abbymath92: "backwards" delta is "del" (more upsidedown really, since delta backwards would really be atled)
TheNecropolist: whatever, it's all Greek to me
loveEstela 222: literally
TheNecropolist: :-)
abbymath92: actually "del" isn't greek
TheNecropolist: stop being technical
Dragonflare211: lol
TheNecropolist: you're ruining the fun
Dragonflare211: pwned
abbymath92: I don't know what it is...someone once said german???
abbymath92: Alex: you want to know how to find the potential function?
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hwangang1337: Yes
TheNecropolist: oh i know how to do that!
abbymath92: that's when you do the set of little integrals
TheNecropolist: don't you just integrate P, Q, and R separately?
Gottmilk423: integrade Pdx, Qdy, and Rdz, right?
TheNecropolist: yeah!
Gottmilk423: integrate*
TheNecropolist: and you figure out that "fun little puzzle"
loveEstela 222: lol
hwangang1337: I got the integrate three things
hwangang1337: How to do after
abbymath92: since del f = F then <del f / del x, del f / del y, del f / del z> = < P, Q, R>
Dragonflare211: how to do after :) lol
Gottmilk423: you combine all the results of the integrals
TheNecropolist: oh you just pick a combination
TheNecropolist: yeah because there's that thing about how yz are just constants to x
loveEstela 222: that fits all of them
TheNecropolist: and so on
hwangang1337: Combine= add?
loveEstela 222: no
Gottmilk423: the ones that are duplicated you only use once in the final equation
Gottmilk423: so for example
abbymath92: gee....you guys don't need me anymore. My work is done! :-D
TheNecropolist: no
TheNecropolist: we need to find out more about the test
Dragonflare211: lol ms brown can u do my hw :)
Gottmilk423: yeah we do
TheNecropolist: chris: she CAN, but she's not going to
TheNecropolist: you have to use the command form
Dragonflare211: whatever
TheNecropolist: ms brown, can you work out a problem on the whiteboard?
TheNecropolist: we haven't used it yet!
Gottmilk423: how about larson #18 and 19?
TheNecropolist: yupes
Gottmilk423: those are the ones i haven't done yet
TheNecropolist: that was what i was thinking :-)
TheNecropolist: me neither
TheNecropolist: jordan, i'll ask for 18, you can ask for 19
Gottmilk423: all right
chejam4: jordan's gottmilk???????
abbymath92: okay...I'll get it on the whiteboard
chejam4: oh like got dank
abbymath92: I'll stay 'til 9, them I'm out...
Gottmilk423: since there are 2 t's in my last name...
Gottmilk423: yeah
TheNecropolist: in our time zone?
HeadISBAgent: lol
chejam4: cool! i gotta go to sleep now good luck everyone on the test
TheNecropolist: by ejames
loveEstela 222: bye
Gottmilk423: haha
abbymath92: http://teachers.sduhsd.k12.ca.us/abrown/Resource s/Whiteboard/VirtualWhiteboard.htm
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abbymath92: which one first?
Dragonflare211: ok i don't get the point of stokes thm...
TheNecropolist: 18
TheNecropolist: I need to see #18, and jordan needs to see #19
abbymath92: okay...18:
TheNecropolist: wait! before you do it i have a quick question
TheNecropolist: you know how fan asked you about the order of u,v thingy today after school?
TheNecropolist: what if that changes an answer becuase we get an extra negative sign or something like that?
abbymath92: if you do ru x rv I won't mark off if that happens to be the wrong in/out/up/down direction
TheNecropolist: so like if we add up all 6 sides
TheNecropolist: and get the wrong answer, you won't mark us down?
oddperson12: will we have to do a 6 sided figure like problem similar to the notes?
abbymath92: if you're doing it all in parametric form
Dragonflare211: so can someone explain to me the point of using stokes them?
Dragonflare211: thm*
TheNecropolist: it's just another short cut
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TheNecropolist: for line integrals (3D)
Dragonflare211: shortcut only if it's in 3D and the figure is closed right?
TheNecropolist: yeah
Dragonflare211: alright
TheNecropolist: Ms. Brown, are you doing 18??? you don't have to explain it, I just want to reference it in case I get stuck.
Gottmilk423: isn't it -z instead of -y in the curl?
abbymath92: is my curl right? I'm getting tired
TheNecropolist: I dont' know, I can't do curl either
Gottmilk423: d/dy (yz) is z, right?
Gottmilk423: yeah
Dragonflare211: blah i can't see this
Dragonflare211: my comp can't load what u post on ur whiteboard
loveEstela 222: shouldn't the second one be 2x-y?
loveEstela 222: nvm
TheNecropolist: no i'ts negative of the second one
abbymath92: the rest should work out pretty well
abbymath92: this one is a little odd since it's acutally easier in rectangular than polar
TheNecropolist: okay
TheNecropolist: thanks
abbymath92: do we still need help w/ 19?
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TheNecropolist: yes!
abbymath92: For 19 use G = x^2 - z
Gottmilk423: haha
ProxRB: sorry, got caught up in all the Chem and piano lessons and all... how have we all been?
TheNecropolist: tired
abbymath92: if you use z - x^2 you'll get the opposite to what they have
ProxRB: which section 19?
Gottmilk423: it makes sense
TheNecropolist: I've been awake for 19 hours
abbymath92: we were looking at this one after school and since the surface is a parabola cylinder the "outward" normal is actually pointing downward
Gottmilk423: since 2 am?
TheNecropolist: yeah
abbymath92: don't stress over this fact.
TheNecropolist: i woke up this morning at 2am
abbymath92: Larson 15.8 (Stokes's) #19
HeadISBAgent: i have a question
loveEstela 222: sometimes the right answer means that you have to do z-f(x) and other times you have to do f(x) -z
loveEstela 222: how can you tell which one to do?
HeadISBAgent: i thought it was always z-f(x) for these
Gottmilk423: it generally is
abbymath92: when in doubt do z - ... so that the z derivative is positive 1
abbymath92: that means the z part is up
Gottmilk423: but we don't lose points if we do the wrong one, right?
loveEstela 222: like on #18
TheNecropolist: yeah, i already asked that
abbymath92: well, if I ask for downward or negative orientation then you do the opposite
abbymath92: positive is always upward or outward
loveEstela 222: ok
HeadISBAgent: i have a question on 16.7 numbers 13 and 23
TheNecropolist: are you using spherical for 13?
HeadISBAgent: i was multiplying 13 by 1/2 and leaving 23 jst as it was instead of leaving 13 and multiplying 23 by 2
HeadISBAgent: i was just wondering y the integral only covers
HeadISBAgent: half the sphere
TheNecropolist: i think that's in the problem
loveEstela 222: yeah the surface is a hemisphere
abbymath92: I need to get going....
TheNecropolist: hemi = half
abbymath92: sorry to leave a couple questions hanging, but you guys are doing a nice job of helping each other out
abbymath92: you're welcome to use the chat room as long as you like...it's always here.
abbymath92: I'll be around in the morning 7:00 - 7:30 for last minute detail type questions.
Gottmilk423: i'll stay for a while and try to help
abbymath92: :-)
Gottmilk423: in spite of my gross incompetence
Gottmilk423: heh
HeadISBAgent: yea but its just the eqn of a sphere isn't it?
abbymath92: thanks to all of you for helping each other
abbymath92: g'nite
HeadISBAgent: nite
TheNecropolist: ms. brown, i'll ask you how to do line integrals tomorrow morning
Dragonflare211: nite
loveEstela 222: bye
HeadISBAgent: wait i got it
ProxRB: bai