How do you use the shell method to set up and evaluate the integral that gives the volume of the solid generated by revolving the plane region y=2x, 2x4 rotated about the x-axis?

1 Answer
Oct 9, 2015

Always graph the constraints first, then determine the correct integration formula.

Explanation:

Here is a graph of the constraints:

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Now, without using calculus, you should visualize rotating this line around the x-axis will generate a cone with radius 2 and height 2. The volume of a cone is:

V=(13)πr2h=(13)π222=(83)π

So, in advance of using calculus, we know the answer is (83)π

Now, using calculus and the shell method :

Because we rotate around the x-axis, integrate with respect to y:

2π02y[4(2y)]dy=(83)π

hope that helped