13. (a) Express \(2 \sin \theta + \cos \theta\) in the form \(R \sin ( \theta + \alpha )\), where \(R\) and \(\alpha\) are constants, \(R > 0\) and \(0 < \alpha < 90 ^ { \circ }\). Give your value of \(\alpha\) to 2 decimal places.
\begin{figure}[h] \end{figure} Figure 4 shows the design for a logo that is to be displayed on the side of a large building. The logo consists of three rectangles, \(C , D\) and \(E\), each of which is in contact with two horizontal parallel lines \(l _ { 1 }\) and \(l _ { 2 }\). Rectangle \(D\) touches rectangles \(C\) and \(E\) as shown in Figure 4. Rectangles \(C , D\) and \(E\) each have length 4 m and width 2 m . The acute angle \(\theta\) between the line \(l _ { 2 }\) and the longer edge of each rectangle is shown in Figure 4. Given that \(l _ { 1 }\) and \(l _ { 2 }\) are 4 m apart,
(b) show that $$2 \sin \theta + \cos \theta = 2$$ Given also that \(0 < \theta < 45 ^ { \circ }\),
(c) solve the equation $$2 \sin \theta + \cos \theta = 2$$ giving the value of \(\theta\) to 1 decimal place. Rectangles \(C\) and \(D\) and rectangles \(D\) and \(E\) touch for a distance \(h \mathrm {~m}\) as shown in Figure 4. Using your answer to part (c), or otherwise,
(d) find the value of \(h\), giving your answer to 2 significant figures.