Jon S. answered 03/09/21
Patient and Knowledgeable Math and English Tutor
Diagonals of a parallelogram bisect each other.
AE = 1/2 of AC = 7
DE = 1/2 of DB = 4
Diagonal of a rhombus are perpendicular so AED forms a right triangle with AE and DE as legs and AD as hypotenuse.
By Pythagorean Theorem AE^2 + DE^2 = AD^2
so AD = sqrt(65)
