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mathcalculus
Group Title
Help with related rate problem please! (DISTANCE)
 11 months ago
 11 months ago
mathcalculus Group Title
Help with related rate problem please! (DISTANCE)
 11 months ago
 11 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)
 11 months ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
which formula do i use?
 11 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
 11 months ago

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

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

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
dy/dt = (dy/dx) * (dx/dt)
 11 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
 11 months ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
i know.
 11 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.
 11 months ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
distance formula?
 11 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)
 11 months ago

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

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

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

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
thanks let me try
 11 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
 11 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,
 11 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.
 11 months ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
and the whole distance formula too.
 11 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
 11 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)
 11 months ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
you just need to find ds/dx
 11 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
 11 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.
 11 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
 11 months ago

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
what about dy?
 11 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.
 11 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
 11 months ago

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
yeah im not sure what's happening.
 11 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)
 11 months ago

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

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

mathcalculus Group TitleBest ResponseYou've already chosen the best response.0
sqrt(x^2+50x+50) ?
 11 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)
 11 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)
 11 months ago

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

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

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

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

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

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
what ?
 11 months ago

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
y=5sqrt(2x+2) y^2 = 50x+50
 11 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
 11 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)
 11 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
 11 months ago

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

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

Coolsector Group TitleBest ResponseYou've already chosen the best response.0
are you sure ?
 11 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)
 11 months ago
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