Câu hỏi 23$\frac{\sin10^\circ+\sin20^\circ}{\cos10^\circ+\cos20^\circ}$ bằng$\tan10^\circ+\tan20^\circ$$\tan30^\circ$$\frac12(\tan10^\circ+\tan20^\circ)$$\tan15^\circ$$\frac14\tan60^\circ$