A square with sides of length 6 cm is given. The boundary of the shaded region is defined by two semi-circles whose diameters are the sides of the square, as shown.
The area of the shaded region is __________ $cm^2$.
By observing the image, we can see that the shaded region consists of two identical semi-circles, but the area where they overlap (the "leaf" shape in the bottom-left corner) is unshaded (white). Thus, the total shaded area is the sum of the areas of the two semi-circles minus twice the area of their overlap.
Let's divide the \( 6 \times 6 \) square into four smaller \( 3 \times 3 \) squares. The intersection of the two semi-circles happens entirely within the bottom-left \( 3 \times 3 \) square.
In the given figure, PQRS is a square of side 2 cm and PLMN is a rectangle. The corner L of the rectangle is on the side QR. Side MN of the rectangle passes through the corner S of the square.
What is the area (in cm²) of the rectangle PLMN?
Note: The figure shown is representative.

A regular dodecagon (12-sided regular polygon) is inscribed in a circle of radius $r$ cm as shown in the figure. The side of the dodecagon is $d$ cm. All the triangles (numbered 1 to 12) in the figure are used to form squares of side $r$ cm and each numbered triangle is used only once to form a square.
The number of squares that can be formed and the number of triangles required to form each square, respectively, are:
Note: The figure shown is representative.