Arrange the numbers increasingly: cos 3, cos 2, cos 1.

First, we'll establish the quadrants that contain the
values,1 , 2, 3.

The first quadrant: (0 ;pi/2), where pi =
3.14, so pi/2 = 1.57

The second quadrant: (pi/2 ;pi)
=> (1.57;3.14)

It is obvious that 1 is in
the interval (0,pi/2), meaning the first quadrant, where the function cosine is
positive,then cos 1>0.

Because 2 and 3 are in the
set (pi/2,pi), then cos2 and cos 3 are negative, because they belong to the second
quadrant, where the values of cosine function are
negative.

So the biggest element is cos
1.

The numbers are arranged in
this way: cos 3, cos 2, cos 1.