$$\frac{1}{2-\cos A}+\frac{1}{2-\cos B}+\frac{1}{2-\cos C}\ge 2$$
Bài 2: Cho $\Delta ABC$. Chứng minh:
$$\frac{\left( 1-\sin \frac{A}{2} \right)\left( 1+\cos \frac{A}{2} \right)}{\sin \frac{A}{2}\left( 1+\sin \frac{A}{2} \right)}+\frac{\left( 1-\sin \frac{B}{2} \right)\left( 1+\cos \frac{B}{2} \right)}{\sin \frac{B}{2}\left( 1+\sin \frac{B}{2} \right)}+\frac{\left( 1-\sin \frac{C}{2} \right)\left( 1+\cos \frac{C}{2} \right)}{\sin \frac{C}{2}\left( 1+\sin \frac{C}{2} \right)}\ge 2+\sqrt{3}$$
Bài viết đã được chỉnh sửa nội dung bởi Stranger411: 24-04-2012 - 19:10