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1. Aug 16, 2004

daveed

i dont really understand when you differentiate both sides of an equation to, for example, time.

like, if you have tan(x)=y/50,
you would get sec^2(x)dx/dt=1/50*(dy/dt)
so does that mean when you differentiate both sides you find the derivative of the whole term and then multiply it by dwhatever/dt?

the book im looking at is just a review for calculus, its only got a short sentence here about this, and its confusing

2. Aug 16, 2004

arildno

Well, both x and y are functions of time.
Hence, you use the chain rule when differentiating the equation

3. Aug 16, 2004

shmoe

Yes, use the chain rule like arildno mentioned. For the problem you gave, you are thinking of x and y as functions of t. You can make this more explicit by replacing "x" with "x(t)" and "y" with "y(t)". The differentiate w.r.t time as normal. When this dependance on t is understood, texts will sometimes supress the (t) part of the notation to make things neater, like the example you gave.

4. Aug 17, 2004

daveed

oh my... lol thankyou im new with calc-learnin it myself this summer-and managed to remember the chain rule wrong. haha thanks guys