this quadrilateral has not sense, because must to serve: DA+CB=DC+AB, but whit data: 4n+6=4n+7 <=> 6=7?
Refer to the diagram of the circle inscribed in a
quadrilateral ABCD with the points of tangency at M, N, P,
and Q. For each positive integer n, a diagram is drawn like
this in which lengths of line segments are
AQ = AM = n,
BM = BN = n + 1,
CN = CP = n + 2, and
DP = DQ = n + 3.
The radius of the circle is , where is a
polynomial function in n.