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How would you determine whether to use dx or dy?
I uploaded a scenario where we revolve around x=6 but we must use dx for the shell method.
2 Answers
$\begingroup$If you are using cylindrical shells method you usually us the opposite variable of what axis you are integrating around, and if you are using disk/washer method, you use the variable of the axis you are rotating around.
$\endgroup$ 2 $\begingroup$It depends. If your function takes in an x input and gives a y output, you have a function of x, which is y = f(x), so you would use dx. If your function takes in a y input and returns an x output, you have a function of y, which is x = f(y), and you would use dy.
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