The most common example of this is to consider an equivalence relation on " X ", with " Y " the set of equivalence classes and " f " the natural projection map.
12.
On the suggestion of Sergeant-Major Henry Ince of the Royal Engineers, he had a tunnel bored from a point above Willis's Battery to communicate with the Notch, a natural projection from the North face.
13.
Where i _ H : H \ to H \ times G is the natural inclusion over the first factor and \ pi _ G : H \ times G \ to G is the natural projection over the second factor.
14.
The category of elements of F comes with a natural projection \ mathop { \ rm el } ( F ) \ to C that sends an object ( A, a ) to A, and an arrow ( A, a ) \ to ( B, b ) to its underlying arrow in C.
15.
A theorem of states that any ring satisfying the first three conditions satisfies the fourth : take ? to be the quotient " K " & times; / " D " & times; of the unit group of " K " by the unit group of " D ", and take ? to be the natural projection.
