\includegraphics{figure_2}
Part of the design of a stained glass window is shown in Fig. 2. The two loops enclose an area of blue glass. The remaining area within the rectangle \(ABCD\) is red glass.
The loops are described by the curve with parametric equations
$$x = 3 \cos t, \quad y = 9 \sin 2t, \quad 0 \leq t < 2\pi.$$
- Find the cartesian equation of the curve in the form \(y^2 = f(x)\). [4]
- Show that the shaded area in Fig. 2, enclosed by the curve and the \(x\)-axis, is given by
$$\int_0^{\frac{\pi}{2}} A \sin 2t \sin t \, dt, \text{ stating the value of the constant } A.$$ [3]
- Find the value of this integral. [4]
The sides of the rectangle \(ABCD\), in Fig. 2, are the tangents to the curve that are parallel to the coordinate axes. Given that 1 unit on each axis represents 1 cm,
- find the total area of the red glass. [4]