Posted by **Mitch** on Friday, December 18, 2009 at 12:42pm.

These questions relate to curvature problems.

a.Explain why (dึ/ds) = (dึ/dt) (dt/ds).

b.Explain why tanึ = dy/dx, which equals (dy/dt) / (dx/dt).

- math -
**bobpursley**, Friday, December 18, 2009 at 1:05pm
I have to assume you know the chain rule.

if x is a function of t, and f is a function of x, then

df/dt=df/dx * dx/dt

this is a fundamental relationship in calculus.

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**Mitch**, Friday, December 18, 2009 at 1:24pm
I understand that much, but I still cannot derive the curvation equation..

a.Let x prime and x double prime be the first derivative and second derivatives of x with respect to t, and similarly for y. Show the following in true.

dณ/ds = ( x y - x y ) / (vector V)^3

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**Mitch**, Friday, December 18, 2009 at 1:26pm
Wow that did not work...

Prove

(dphi/ds) = ( xprime*ydouble prime - xdoubleprime*yprime ) / (vector V)^3

- math -
**Mitch**, Friday, December 18, 2009 at 2:26pm
Help?

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**bobpursley**, Friday, December 18, 2009 at 4:41pm
x prime. OK that is the first derivative of x with respect to ???

same for double prime. Your statement is just totally meaningless, it cant be proved unless it is understood.

- math -
**Mitch**, Friday, December 18, 2009 at 8:31pm
I am trying to prove the formula..

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