- #1

daster

Say we have two functions of x, v and y, such that v=x+y. How can I find v'?

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- Thread starter daster
- Start date

- #1

daster

Say we have two functions of x, v and y, such that v=x+y. How can I find v'?

- #2

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Why doncha differentiate its definition wrt to "x"??

Daniel.

PS.Tell me what u get.

Daniel.

PS.Tell me what u get.

- #3

HallsofIvy

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Use the chain rule: v= x+ y so dv/dx= dx/dx+ dy/dx= 1+ dy/dx. What dy/dx is depends, of course, on what function y is of x.

- #4

daster

Oh, so it's only dy/dx? Cause I remember my book doing something like (dy/dx)(dv/dx) or something. Thanks HallsofIvy.

Another question. How do I find d(e^u dy/dx)/du, where u and y are functions of x?

My book says:

[tex]e^u \frac{dy}{dx} + e^u \frac{d^2y}{dx^2} \cdot \frac{dx}{du}[/tex]

I understand this is the product rule, but where'd the dx/du come from?

Another question. How do I find d(e^u dy/dx)/du, where u and y are functions of x?

My book says:

[tex]e^u \frac{dy}{dx} + e^u \frac{d^2y}{dx^2} \cdot \frac{dx}{du}[/tex]

I understand this is the product rule, but where'd the dx/du come from?

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- #5

Galileo

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[tex]\frac{d}{du} \frac{dy}{dx}=\frac{d^2y}{dx^2}\frac{dx}{du}[/tex]

- #6

daster

Dank je.

- #7

Galileo

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Graag gedaan.

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