9.

\begin{tikzpicture}[scale=0.8, >=stealth]
    % Draw the axes
    \draw[->] (-0.5, 0) -- (13, 0) node[right] {$x$};
    \draw[->] (0, -3) -- (0, 3) node[above] {$y$};
    
    % Label the origin
    \node[below left] at (0,0) {$O$};

    % Draw the curve C: y = cos(x/12)
    % We scale the x-axis such that x = 12*pi corresponds to 6 units on the TikZ grid.
    % The function plotted is y = cos(pi * x / 6)
    \draw[thick, domain=0:12, samples=100] plot (\x, {2*sin(deg(\x*pi/6))});
    
    % Label the curve C
    \draw[dashed] (0,1.5) -- ({asin(1.5/2)/30}, 1.5) --  ({asin(1.5/2)/30}, 0) node[below] {$\alpha$};
    \node[left] at (0,1.5) {$k$};
    % Mark and label the minimum point M
    % M is at x = 12*pi (scaled to 6), y = cos(pi) = -1
    \fill (9, -2) circle (2pt);
    \node[below] at (9, -2) {$M$};
\end{tikzpicture}

Figure 5 shows a sketch of part of the curve $C$ with equation $y = \sin \left( \frac { x } { 12 } \right)$, where $x$ is measured in radians. The point $M$ shown in Figure 5 is a minimum point on $C$.
\begin{enumerate}[label=(\alph*)]
\item State the period of $C$.
\item State the coordinates of $M$.

The smallest positive solution of the equation $\sin \left( \frac { x } { 12 } \right) = k$, where $k$ is a constant, is $\alpha$. Find, in terms of $\alpha$,
\item \begin{enumerate}[label=(\roman*)]
\item the negative solution of the equation $\sin \left( \frac { x } { 12 } \right) = k$ that is closest to zero,
\item the smallest positive solution of the equation $\cos \left( \frac { x } { 12 } \right) = k$.
\end{enumerate}\end{enumerate}

\hfill \mbox{\textit{Edexcel P1 2019 Q9 [4]}}