p1=plot(sin(x), (x, -7, 7), ticks=pi/2,gridlines=True, tick_formatter=pi, axes_labels=['$x$','$y$'], fontsize=14, color='blue')
p2=plot(sin(0.5*x), (x, -7, 15), ticks=pi/2,gridlines=True, tick_formatter=pi, axes_labels=['$x$','$y$'], fontsize=14, color='red')
show(p1+p2)