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mathcalculus
Group Title
Help with related rate problem please! (DISTANCE)
 9 months ago
 9 months ago
mathcalculus Group Title
Help with related rate problem please! (DISTANCE)
 9 months ago
 9 months 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)
 9 months ago

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
right.
 9 months ago

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

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

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
distance formula?
 9 months 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)
 9 months ago

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
right.
 9 months ago

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

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

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

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
and the whole distance formula too.
 9 months 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
 9 months 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)
 9 months ago

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
are you sure ?
 9 months 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)
 9 months ago
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