$1)\sin A+\sin B+\sin C\leq \frac{3\sqrt{3}}{2}$$2)\cos A+\cos B+\cos C\leq \frac{3}{2}$ ABC là tam giác nhọn$3)\tan A+\tan B+\tan C\geq 3\sqrt{3}$ ABC là tam giác nhọn$4)\cot A+\cot B+\cot C\geq \sqrt{3}$ ABC là tam giác nhọn$5)\sin^2A+\sin^2B+\sin^2C\leq \frac{9}{4}$$6)\sin A\sin B\sin C\leq \frac{3\sqrt{3}}{8}$$7)\cos A\cos B\cos C\leq \frac{1}{8}$$8)\sin\frac{A}{2}\sin\frac{B}{2}\sin\frac{C}{2}\leq \frac{1}{8}$$9)\cos\frac{A}{2}\cos\frac{B}{2}\cos\frac{C}{2}\leq \frac{3\sqrt{3}}{8} $$10)\tan\frac{A}{2}\tan\frac{B}{2}\tan\frac{C}{2}\leq \frac{1}{3\sqrt{3}}$