Wry neck, or torticollis, is a painfully twisted and tilted neck. The top of the head generally tilts to one side while the chin tilts to the other side. This condition can be congenital (present at birth) or acquired. It can also be the result of damage to the neck muscles or blood supply. Wry neck sometimes goes away without treatment.
In the quaternions, 0 is the additive identity. In the ring of functions from R to R, the function mapping every number to 0 is the additive identity. In the additive group of vectors in Rn, the origin or zero vector is the additive identity.
1 Identity function is injective and hence its inverse exists, which is also identity function. 2  The graph of an invese of an identity function is also same as the graph of an identity function. 3  The slope of the graph of identity function is 1.  The graph of an identity function is same as the graph of y = x.