Final answer:
The length of AC, which is one of the sides of the square, is equal to the length of any other side of the square.
Step-by-step explanation:
A square has four equal sides. Let's label the vertices of the square as A, B, C, and D.
The length of AC, which is one of the sides of the square, is equal to the length of any other side of the square.
Therefore, the length of AC is equal to the length of AB, BC, or CD.
This means that to find the length of AC, you just need to measure one of the sides of the square.