3.18 Blog Post
- Identify the difference between rotating around a vertical line and a horizontal line.
- When rotating around the x-axis, the important variable is y because it becomes the radius of the figure being formed. When rotating around the y-axis, the important variable is x because it becomes the radius of the former figure.
- What is the difference between creating a washer and a disk?
- When a washer is created, the two radii must be subtracted from each other in order to find the volume of the the existing figure. When a disk is created, there is only one radius for the whole figure so it is not necessary to subtract.
- Identify two examples that use rotating about a vertical line and a horizontal line.
Example #1:
Example #2:
Think about your example. You have split your area with x = 1. but unfortunately, you do not make it a washer. It is solely a disk in your picture... but there is an inner radius of 1.
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