geometry
posted by *** .
if ac=17 and bd=15 nd ab=11.2 what is the area of the rhombus

The area of a rhombus is half the product of the diagonals.
So, a = 1/2 * 17 * 15 = 127.5
the length of ab is redundant; specifying the diagonals takes care of that, since they are perpendicular and bisect each other.