In general, a rectangle does not have an incenter.
The incircle must be tangent to all sides of the polygon.
Does a square have an incenter?
(a)Yes, because in square, there is a circle which touches all the sides internally and the diagonals intersect at a point, this point is the incenter of the circle.
What is incenter of a square?
The point where the interior angle bisectors intersect.
