Rectangle ABCD: Proving Diagonal Equality in Quadrilaterals

To solve this problem, we'll follow these steps:

• Identify the diagonal lines of the rectangle $AC$ and $BD$.
• Apply the diagonal property theorem for rectangles.

Let's go through the solution:

A rectangle in Euclidean geometry has several properties, one of which is that its diagonals are equal in length. This can be derived from the fact that opposite sides of a rectangle are equal and parallel, making it a specific type of parallelogram. Thus, both diagonals split the rectangle into congruent triangles, ensuring they are of equal length.

For rectangle $ABCD$, diagonals $AC$ and $BD$ must be equal due to this inherent geometric property.

Therefore, the statement that "the diagonals of rectangle ABCD are equal" is True.