fig,ax = plt.subplots(figsize = (10,6))
ax.plot(x,c,color='red',lw=2,ls='--',label = 'cosine')
ax.plot(x,s,color='green',lw=2,ls=':',label = 'sine')
# ax.set_xticks((-np.pi, -np.pi/2, 0, np.pi/2, np.pi),(1, 2, 3, 4, 5));
ax.set_xticklabels((r'$-\pi$', r'$-\pi/2$', r'$0$', r'$+\pi/2$', r'$+\pi$'));
# ax.set_yticks((-1, 0, +1),(r'$-1$', r'$0$', r'$+1$'));
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')
ax.xaxis.set_ticks_position('bottom')
ax.spines['bottom'].set_position(('data',0))
ax.yaxis.set_ticks_position('left')
ax.spines['left'].set_position(('data',0))
ax.legend(loc='lower left')
t = 2*np.pi/3
ax.plot([t,t],[0,np.cos(t)], color ='blue', linewidth=2.5, linestyle="--")
ax.scatter([t,],[np.cos(t),], 1000, color ='blue')
ax.annotate(r'$\sin(\frac{2\pi}{3})=\frac{\sqrt{3}}{2}$',
xy=(t, np.sin(t)), xycoords='data',
xytext=(+10, +30), textcoords='offset points', fontsize=16,
arrowprops=dict(arrowstyle="->", connectionstyle="arc3,rad=.2"))
ax.plot([t,t],[0,np.sin(t)], color ='red', linewidth=2.5, linestyle="--")
ax.scatter([t,],[np.sin(t),], 50, color ='red')
ax.annotate(r'$\cos(\frac{2\pi}{3})=-\frac{1}{2}$',
xy=(t, np.cos(t)), xycoords='data',
xytext=(0, -90), textcoords='offset points', fontsize=16,
arrowprops=dict(arrowstyle="->", connectionstyle="arc3,rad=.2"));
for label in ax.get_xticklabels() + ax.get_yticklabels():
label.set_fontsize(16)
label.set_bbox(dict(facecolor='white', edgecolor='None', alpha=0.65 ))