The meaning of the sets in the figures is explained BELOW each figure.
For example, the first sketch is intended to HELP you to understand the relation between a set  C,  its image, and the pre-image of the image.
There is further discussion of the second sketch below the second sketch.

The second sketch shows how a subset  D  of the codomain of a function is “pulled-back” to a subset of the domain (the pre-image) and then shows how this pre-image is “pushed-forward” to give the image of the pre-image.

Last modified Mar 21, 2008

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