A weighted pendulum swings back and forth freely and its horizontal position is plotted against time. The resulting plot appears as a cosine wave: B 0 0.20 metres +x C B Figure 1 - Horizontal position of a pendulum plotted against time. The pendulum swings from A to C through position B, then returns to A through B again. The pendulum completes two full cycles in one second and the horizontal distance of the pendulum swing is 0.20 m. a) Write a function, x(t), for the horizontal position of the pendulum in terms of a cosine wave. b) Calculate the speed at which the pendulum passes the midpoint (B). (3) (3) (6 marks)