Hello, the original title is: cut an inch square from the corner of this 5 inch square. What is the area of the largest square that can fit in the remaining space? Cut a square with a side length of 1 inch from the four corners of this square with a side length of 5 inches. What is the area of the largest square that can be put down in the remaining drawings?

In fact, this question is to ask you to calculate the area of the oblique square in the picture below: