Find the angle of an intersection between diagonals of a rectangle with sides 6 and 4 

 ABCD is a rectangle. Find the length of each diagonal.  

Which property makes a rectangle a special type of parallelogram?

a. The opposite angles are congruent.

b. The diagonals are congruent.

c. The opposite sides are parallel.

d. The consecutive sides are congruent.

The length ℓ of a rectangle is decreasing at a rate of 9 cm/sec while the width w is increasing at a rate of 9 cm/sec. When ℓ=15 cm and w=8​cm, find the rates of change of the​ area, the​ perimeter, and the lengths of the diagonals of the rectangle. Determine which of these quantities are​ increasing, decreasing, or constant.