A rectangle is to be inscribed in a semicircle of radius 5 $\mathrm{cm}$ as shown in the figure.
(a) Show that the area of the rectangle is modeled by the function
$$A(\theta)=25 \sin 2 \theta$$
(b) Find the largest possible area for such an inscribed rectangle.
(c) Find the dimensions of the inscribed rectangle with the largest possible area.