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Chain rule

• To: mathgroup at smc.vnet.net
• Subject: [mg24562] Chain rule
• From: "Claude" <fran_claude at hotmail.com>
• Date: Mon, 24 Jul 2000 03:04:46 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hello,

I am just trying to solve:
dy/dx when x = 2t + 5 and y = 2t^2 - 1.

Can it be done directly by Mathematica or do I have to solve dy/dt and
dx/dt and finally divide dy/dt by dx/dt?

I tried posing x = 2t + 5 and y = 2t^2 - 1 and ask solve for D [y,x], but
that does not evaluate properly (the answer is 2t).  I would have thought
that Mathematica would have used the chain rule automatically.

Thanks for your help,