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mathcalculus
Group Title
Help with related rate problem please! (DISTANCE)
 one year ago
 one year ago
mathcalculus Group Title
Help with related rate problem please! (DISTANCE)
 one year ago
 one year ago

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Coolsector Group TitleBest ResponseYou've already chosen the best response.0
hint > you want dy/dt so: dy/dt = (dy/dx) * (dx/dt)
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
which formula do i use?
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
you have dx/dt at this point and you have the point itself. that should help you
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
right.
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
got that.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
dy/dt = (dy/dx) * (dx/dt)
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
dy/dx means derivative of y with respect to x dx/dt is given at this point
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i know.
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
but what formula should i use, for example there are problems for volume, circle, triangle, etc.
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
distance formula?
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
ok so distance from the origin is s = sqrt(x^2 + y^2) so you want ds/dt = (ds/dy) * (dy/dt) + (ds/dx) * (dx/dt)
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
what does s symbolize?
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
right.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
s  distance
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
so that is it. now you have it all
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
thanks let me try
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
you can, as well, to express y in terms of x in the distance formula and then find ds/dt = (ds/dx) * (dx/dt) it will be much more simple
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
right the whole 5*sqrt(2x+2) is throwing me off though,
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
im not sure if i should find the derivative of that function with respect to time.
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
and the whole distance formula too.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
ok so if we do it the way i said at the end : "you can, as well, to express y in terms of x in the distance formula and then find ds/dt = (ds/dx) * (dx/dt) it will be much more simple" then you dont have to do much
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
cause s=sqrt(x^2 + y^2) = sqrt(x^2+50x+50) now ds/dt = (ds/dx) * (dx/dt)
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
you just need to find ds/dx
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i did this: i found s=10.0499 then i found the derivative which i got 5/sqrt(2x+2) *dx/dt
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i got ds/dt as 10 but i know it's wrong.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
you dont need to find s. you need to find ds/dx
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
ds/dx=10
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
what about dy?
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
since we express y in terms of x we dont need to worry about it anymore.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
ds/dx = (x + 25)/sqrt(x^2+50x+50) at the point x=1 it is ds/dx = 26 / sqrt(101) so ds/dt = (26 / sqrt(101))* 4 i might done some mistake though
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
yeah im not sure what's happening.
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
why? s = sqrt(x^2+y^2) = sqrt(x^2+50x+50) so we want ds/dt ds/dt = ds/dx * dx/dt ds/dx = (x + 25)/sqrt(x^2+50x+50) ds/dx at this point = 26/sqrt(101) so ds/dt at this point = 26 * 4 /sqrt(101)
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
plugged into the derivative x=1 and dx/dt = 4
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
understand what i did ?
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
sqrt(x^2+50x+50) ?
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
this is the distance.. s=sqrt(x^2 + y^2) = sqrt(x^2 + 50x + 50)
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i know, how'd you come up with this sqrt(x^2+50x+50)
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
x^2+50x+50)
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
plugged y=5sqrt(2x+2)
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
10=10
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
50x+50?
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i plugged in y and x
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
y=5sqrt(2x+2) y^2 = 50x+50
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
plugged y=5sqrt(2x+2). i plugged in y and x. 10=10
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
so now s = sqrt(x^2 + y^2) but since y^2 = 50x+50 s = sqrt(x^2+50x+50)
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
not the value of y at the point. plug y as a function of x
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
okay thanks alot.
 one year ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i got it
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
are you sure ?
 one year ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
s = sqrt(x^2+y^2) = sqrt(x^2+50x+50) so we want ds/dt ds/dt = ds/dx * dx/dt when we calculate ds/dx we calculate is using s as a function of x. not plugging numerical values yet. ds/dx = (x + 25)/sqrt(x^2+50x+50) now plug x=1 ds/dx at this point = 26/sqrt(101) so ds/dt at this point = 26 * 4 /sqrt(101)
 one year ago
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