Volumes of Revolution

Rotation About the x-axis

Integration can be used to find the area of a region bounded by a curve whose equation you know. If we want to find the area under the curve y = x² between x = 0 and x = 5, for example, we simply integrate x² with limits 0 and 5.
Now imagine that a curve, for example y = x², is rotated around the x-axis so that a solid is formed. The volume of the shape that is formed can be found using the formula:

Rotation about the y-axis

If the body is rotated about the y-axis rather than the x-axis, then we use the formula:

Revision Guides; MathsRevision.Net Home

© Matthew Pinkney 2007