Suppose that a point is moving along the path xy=1

so that

dy/dt= 3.

Find dx/dt when x = 1.

dx/dt =?

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- Nov 3rd 2010, 04:48 PM #1

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- Nov 3rd 2010, 05:13 PM #2

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- Nov 3rd 2010, 05:15 PM #3

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You need to use a product rule $\displaystyle \frac{d}{dt}(xy)=\frac{d}{dt}(1)$

$\displaystyle \frac{dx}{dt}y + x\frac{dy}{dt} = 0$ (chain rule on the inside because this is with respect to t)

You are given x = 1 so then (1)(y)=1

y=1

substitute all the values in and solve for $\displaystyle \frac{dx}{dt}$ this is part of related rates if you'd like to read in your calculus textbook to clear up any thing you're confused about.

- Nov 3rd 2010, 05:39 PM #4

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- Nov 3rd 2010, 05:43 PM #5

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