difference between disc and washer with examples...i just wanna understand this topic

Question

anonymous · Answer

The disk method involves a region of integration that "touches" the axis of revolution. The washer method allows for a region of integration that doesn't.

For example, look at the following image: Say you want to find the volume of the solid generated by the revolution of the region bounded by the line $y=cx+d$ and the x-axis, over $[0,2]$, revolved about the x-axis (y = 0). Since the region touches the axis of revolution, revolving the area one point at a time forms multiple disks.
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