slicing method (1 Viewer)

[kr73114]

how do u know if the disk is annulous (whether to use washer method or disk method)?

 

[Drongoski]

how do u know if the disk is annulous (whether to use washer method or disk method)?

Unless directed to use one or the other, choose method easier to you or the one that makes the solution easier.

 

[kr73114]

Unless directed to use one or the other, choose method easier to you or the one that makes the solution easier.

soz wrong question...how do u know if the volume is annulous?
you know with the big radius minus the small radius
sorry cant explain properly

 

[Drongoski]

Best is to post a question or 2.

 

[kr73114]

1) use the method if slicing to find the volume of the solid obtained by rotating the region enclosed between the curves y=4-x^2 and the lines x=2 and y=4 through one complete revolution about
a) the x-axis b)the y axis c)the line x=2 d)the line y=4
thanks

 

[Drongoski]

Easy 4 cases - ideal using slicing.

 

[XTsquared]

annulus = gap in between. If no gap (obvious after drawing or recognising) then no annulus, if gap then annulus. If it's really that difficult for you, just use the annulus way (R^2 - r^2) and the small radius (r) should be 0 if it's not an annulus (as it will be constant1 - constant1). Hope that helps.

 

[Drongoski]

Are the answers??: