Things to Remember When Approaching Related Rates Problems:Make sure to first determine all that you know about a situation, i.e. determine what quantities are changing and which ones are fixed. It is best to draw various diagrams in certain cases. Write down any rates given to you as derivatives in Leibnitz's notation. Then determine what the question is asking for. If it is a rate then is there a particular moment they want the rate for or is it just an expression? If you are not using implicit differentiation then try and get the "setup" as I described it by making the rate you want equal to a product of two rates, one given and one to be determined. If you are using implicit differentiation then make sure you are differentiating with respect to the desired variable (in most cases time).
Friday, February 20, 2009
Homework due 02/24/09
Do problems 18, 19 and 21 on page 212 of your textbook.
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2 comments:
for 21, how do you solve for dR/dL if you aren't given information to make an equation for R in terms of L (except you know that R decreases as L increases)?
So you are wondering where to find an equation that relates the length L of the cylinder and the radius r. Well, ask yourself whether any clay is lost or not. If the amount of clay is the same then what quantity of the cylinder never changes? It will be this quantity that will help you get an equation. Think of all the things that you know about a cylinder and which quantity remains constant in this case no matter how thick or thin this cylinder is.
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