geometry
posted by rocio .
in a parallelogram abcd=28,bc=45,and ac=53. is the parallelogram a rectangle?

I don't understand
abcd = 28
I will assume that 28 and 45 are two of the sides and 53 is the diagonal.
If it it a rectangle,
28^2 + 45^2 = 53^2
2809 = 2809 , true, so yes it is a rectangle