<s>[INST] Prove: $\frac{a}{m_a}+\frac{b}{m_b}+\frac{c}{m_c}\ge 2\sqrt{3}$ Let $a,b,c$ be the lengths of the sides of triangle $ABC$ opposite $A,B,C$, respectively, and let $m_a,m_b,m_c$ be the lengths of the corresponding angle medians. Prove:
$$\frac{a}{m_a}+\frac{b}{m_b}+\frac{c}{m_c}\ge 2\sqrt{3}.$$
Source: I thought about it while solving the American Mathematical Monthly's problem 11945, which asked to prove $\frac{a}{w_a}+\frac{b}{w_b}+\frac{c}{w_c}\ge 2\sqrt{3}$, where $w_a,w_b,w_c$ are respective angle bisectors.
I think it can be solved by making up (inequality-) constrained optimization problem, but I am interested in solution within elementary geometry.
 [/INST] Another way.
By the Ptolemy and C-S twice we obtain:
$$\sum_{cyc}\frac{a}{m_a}=\sqrt{\sum_{cyc}\left(\frac{a^2}{m_a^2}+\frac{2ab}{m_am_b}\right)}\geq\sqrt{\sum_{cyc}\left(\frac{a^2}{m_a^2}+\frac{2ab}{\frac{c^2}{2}+\frac{ab}{4}}\right)}=$$
$$=2\sqrt{\sum_{cyc}\left(\frac{a^2}{2b^2+2c^2-a^2}+\frac{2ab}{ab+2c^2}\right)}=2\sqrt{\sum_{cyc}\left(\frac{a^4}{2a^2b^2+2a^2c^2-a^4}+\frac{2a^2b^2}{a^2b^2+2c^2ab}\right)}\geq$$
$$\geq2\sqrt{\frac{(a^2+b^2+c^2)^2}{\sum\limits_{cyc}(4a^2b^2-a^4)}+\frac{2(ab+ac+bc)^2}{\sum\limits_{cyc}(a^2b^2+2c^2ab)}}\geq2\sqrt{1+2}=2\sqrt3.$$
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