Triangle Inequation proof
22237
Proof of triangle inequality
89493
Prove that circumcentre of $ABH,BCH,CAH$ are the vertices of a triangle congruent to $ABC$
61343
Prove that if $\alpha, \beta, \gamma$ are angles in triangle, then $(tan(\frac{\alpha}{2}))^2+(tan(\frac{\beta}{2}))^2+(tan(\frac{\gamma}{2}))^2\geq1$
61483
Prove the following identity combinatorially
75356
Show that the area of a triangle is given by this determinant
89838
Prove that $3 \le a+b+c \le 2\sqrt{3}$ in a triangle
90904
Combinatorial proof of an identity with squared binomial coefficients
65983
Combinatorial proof of binomial coefficient summation identity
55975
Let $a$, $b$ and $c$ be the three sides of a triangle. Show that $\frac{a}{b+c-a}+\frac{b}{c+a-b} + \frac{c}{a+b-c}\geqslant3$.
108704
Help with proof of $|x+y| \geq |x|-|y|$
54170
Prove that $\triangle ABC$ is equilateral, If $(a+b-c)^{a}\cdot (b+c-a)^{b}\cdot (c+a-b)^{c}\geq a^a\cdot b^b\cdot c^c$
71564
Combinatorial proof of identity involving central binomial coefficients
145783
How can I prove this inequality in a triangle: $\frac{1}{(b+c-a)} +\frac{1}{(c+a-b)} +\frac{1}{(a+b-c)} \gt \frac{1}{a} +\frac{1}{b} +\frac{1}{c}$?
45702
For any triangle with sides $a$, $b$, $c$, show that $a^2b(a-b)+b^2c(b-c)+c^2a(c-a)\ge 0$
103806
How to prove triangle inequality for $p$-norm?
83034
Triangle inequality square #2
12646
In acute angle triangle, prove that $\cos (A-B) \cos (B-C) \cos (C-A)\ge 8\cos A \cos B \cos C$