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here is y = cos^-1x = arccosx and its graph:
open this image:
http://img23.imageshack.us/f/arccos3.gif/
Since {y = cos^-1(x) is the

of the function

, the function y = cos^-1(x)

and



.
But, since

is

, its

must be restricted in order that y = cos^-1(x) is a function.
To get the graph of y = cos^-1x, start with a graph of

.

the

of the function to a one-to-one region - typically [

,

] is used for cos^ -1x. This leaves the range of the restricted function unchanged as [

,

].
Reflect the graph across the line

to get the graph of y = cos^-1 x y = arccos x, the black curve at right on the graph above.
Notice that y = cos^-1x has domain [

,

] and range [

,

]. It is strictly decreasing on its entire domain.