Thread: Volume of Revolution: Disk Method

I just want to make surer the answer to the following question given by my text is not correct.

The question is:

Use the disk method to find the volume of a solid bounded by the curves y=2x^2, y=3,y=4 about the x-axis.

My textbook says the answer is: 58.33

I disagree with this.

Can someone check for me please.

Thank you.

Originally Posted by taitai

I just want to make surer the answer to the following question given by my text is not correct.

The question is:

Use the disk method to find the volume of a solid bounded by the curves y=2x^2, y=3,y=4 about the x-axis.

My textbook says the answer is: 58.33

I disagree with this.

Can someone check for me please.

Thank you.

And what did you get as an answer? Show your working...

Are you counting BOTH sides of the y-axis?

Originally Posted by TKHunny

Are you counting BOTH sides of the y-axis?

I tried the cylindrical shells method

2 times the answer gives the 58.33 but it says sue the disk method which i tried and did not get 58.33.

@Prove it, I never said anything about you showing me the work, I just need confirmation that by the disk method we don't get 58.33.

I didn't think that was hard to understand.

Originally Posted by taitai

@Prove it, I never said anything about you showing me the work, I just need confirmation that by the disk method we don't get 58.33.

I didn't think that was hard to understand.

You should check your attitude at the door.


Maybe I'm wrong, but you seemed to ask why you didn't get the right answer.

I can confirm that the book's answer is correct ... and you are wrong.

There! . . . My job is done.

Originally Posted by taitai

I tried the cylindrical shells method

2 times the answer gives the 58.33 but it says sue the disk method which i tried and did not get 58.33.

@Prove it, I never said anything about you showing me the work, I just need confirmation that by the disk method we don't get 58.33.

I didn't think that was hard to understand.

And is it hard to understand that we cannot help you find you error or whatever without seeing how you have tried to implement the method. Or are you proposing going about getting help by the twenty questions method.


CB