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Posts: 3732

Posts: 2598

You should study from the book or speak with a TA/professor/tutor in real life. We will add no value by just explaining the problem to you. You will only learn by studying harder or talking with someone who can actively ask you questions and see what you already understand, which is difficult to do online.

Go study more, and if you need extra help see someone who knows what they're talking about and is willing to help you, not just show you the answer. It's a pain in the ass, but you will be better off in the long run.

Posts: 5631

DURP, I'M 12 WHAT IS THIS?

Posts: 1475

I did this about a month ago. I believe you have to find the derivative of the formula for volume of a cone, with some of those variables plugged in.

Posts: 534

It might help if you eat a hotpocket...

Posts: 1251

You know how much the volume is changing/minute, so change that into how much the radius is changing per minute.

Take that, get the derivative and sub in the time, or something like that.

Posts: 279

Uh. I got dh/dt = 0.671 and dr/dt = 0/895 but i havent done those since like before christmas. Thanks for the refresher though. AP Calc test coming up soon. praying for a 5 or 4.

Posts: 3915

calculus is too fucking hard. fuck that class.

Posts: 1126

and to think i used to be able to do this, now i have no idea.

Posts: 943

dude write it out. the pics to small for my blackberry. otherwise figure it from ur txtbook, or pay attn in class,

Posts: 5379

Calculus = Asain People Talk

Posts: 634

im 13 am in geometry pre ib and am tired of looking at numbers....i am on spring break

Posts: 6288

sweet post loser

Posts: 138

YouTube, seriously. Just search key words in the problem, or the name of what section of calc you're in, and get learned! I aced my last calc test by watching videos of how to do problems.

Posts: 250

damn thats a good idea!

Posts: 2021

r(t) === will be the radius of your cone. This radius various in function of time (thats why I put (t))

V=(Pi*(r^2)*h)/3=(Pi*(r^2)*(3r/4))/3=(Pi*(r^3))/4 === Thats the volume of your cone (h=3d/8=3r/4).

V(t)=(Pi*(r(t)^3))/4 ===(1) Your volume and radius are both various in vonction of time.

r(0)=8/3 m === Your initial radius

V(0)=(Pi*((8/3)^3))/4= (128*Pi)/27 === Your initial volume

V(t)=V(0)+V.dot= (128*Pi)/27 +15*t ===(2) This is the equation of your volume in function of time

Take equations (1) and (2) togetter:

(128*Pi)/27 +15*t=(Pi*(r(t)^3))/4 === From this point all you need is to isolate your function r(t)

r(t)^3=512/27+60t/Pi

r(t)=(512/27+60t/Pi)^1/3 === You now have to derive this then its kidna over

To derive this use the substitution

u(t)=512/27+60t/Pi === Remember that: du/dt=60/Pi ...... and dt/du=Pi/60 (we'll use that later)

You'll have:

r(u)=u^1/3

dr/du=(1/3)*(u^-2/3) === Remember that: dr/du=(dr/dt)*(dt/du) and you will find:

(dr/dt)*(Pi/60)==(1/3)*(u^-2/3)=(1/3)*((512/27+60t/Pi)^-2/3)

dr/dt=(20/Pi)*((512/27+60t/Pi)^-2/3)

Thats what we were looking for!! They asked for the speed when h=2 meters... and when h=2 meters r=8/3 m thats when time t=0...

dr/dt=(20/Pi)*((512/27+0)^-2/3)=0,1111905573 m/min=11,12 cm/min

if you want to know the rate after 5min t=5 min, plug it in

r(t) === will be the radius of your cone. This radius various in function of time (thats why I put (t))

V=(Pi*(r^2)*h)/3=(Pi*(r^2)*(3r/4))/3=(Pi*(r^3))/4 === Thats the volume of your cone (h=3d/8=3r/4).

V(t)=(Pi*(r(t)^3))/4 ===(1) Your volume and radius are both various in vonction of time.

r(0)=8/3 m === Your initial radius

V(0)=(Pi*((8/3)^3))/4= (128*Pi)/27 === Your initial volume

V(t)=V(0)+V.dot= (128*Pi)/27 +15*t ===(2) This is the equation of your volume in function of time

Take equations (1) and (2) togetter:

(128*Pi)/27 +15*t=(Pi*(r(t)^3))/4 === From this point all you need is to isolate your function r(t)

r(t)^3=512/27+60t/Pi

r(t)=(512/27+60t/Pi)^1/3 === You now have to derive this then its kidna over

To derive this use the substitution

u(t)=512/27+60t/Pi === Remember that: du/dt=60/Pi ...... and dt/du=Pi/60 (we'll use that later)

You'll have:

r(u)=u^1/3

dr/du=(1/3)*(u^-2/3) === Remember that: dr/du=(dr/dt)*(dt/du) and you will find:

(dr/dt)*(Pi/60)==(1/3)*(u^-2/3)=(1/3)*((512/27+60t/Pi)^-2/3)

dr/dt=(20/Pi)*((512/27+60t/Pi)^-2/3)

Thats what we were looking for!! They asked for the speed when h=2 meters... and when h=2 meters r=8/3 m thats when time t=0...

dr/dt=(20/Pi)*((512/27+0)^-2/3)=0,1111905573 m/min=11,12 cm/min

if you want to know the rate after 5min t=5 min and just plug your time in dr/dt=...

Posts: 4696

Fuck related rates

Posts: 943

cool, just dont complain when someone who found calculus easy drives by you in a ferrari later in life because he helps build the computer you are using to talk shit about calc.

Posts: 3915

you are a dick.

Posts: 2075

Stupid comment asshole

Posts: 1797

Posts: 943

haha, guess math isnt your thing either. No ferrari for you as well

Posts: 943

haha nice,,, its funny to think that if that guy in the picture does actually know enough about computers, hes gonna end up better off than you. what does cccp stand for? The suck 3 cocks a day party?

Posts: 943

whats wrong with nerds?

Posts: 11251

hahaha you guys are all alike, broken fucking records

Posts: 101

Related rates have absolutely nothing to do with circuitry. For all we know the OP blows at precalc, but triple integrals and greene's are no big deal.

Posts: 943

sorry im just sick of people complaining about math... i dont know what else to say, the teachers must suck in this country.

Posts: 5675

I am a computer engineering student, so I can safely say, "go fuck yourself, you are giving us a bad name."

Did that explanation above work for you OP? If not, I'll take a look at it...

Did that explanation above work for you OP? If not, I'll take a look at it...

Posts: 943

fair enough, but who do you mean by "us" ? Are you hoping to work at the geek squad at best buy or something?

Posts: 5675

lol funny shit man. Yeah Geek Squad. Thats all I hope for. Why would I use my degree to work for Intel or Google, when I could work for $12 an hour fixing octogenarians' computers?

ha I know you are just fucking with me though...

ha I know you are just fucking with me though...

Posts: 943

cool man well hit me up when you start working at google

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