Draw the related diagram:
\
and
.
Consider function
on interval
.
Maximize
, minimize
.
.
Derivative on each side with respect to
.


Derivative of inverse trigonometric formula:
.




.
Find the critical numbers by equating derivative to zero.
\

.
The solutions of
are





.
and
.
The critical numbers are
and
.
is not in the interval
.
The critical number is
.

Substitute
.

.
The function
has minimum at
.
Therefore,
is maximum at
.
Substitute
in
.



.
The absolute maximum is
.
is maximum at
.
is maximum at
.