In $\Delta ABC$ if $a^2+b^2+c^2-ac-\sqrt{3}ab=0$ Then Prove that Triangle is Right angled
216
In a $\triangle ABC,a^2+b^2+c^2=ac+ab\sqrt3$,then the triangle is
151607
Show that  $A\Delta B = C$ if and only if $A = B\Delta C$
137864
Prove that $ \left(1+\frac a b \right) \left(1+\frac b c \right)\left(1+\frac c a \right) \geq 2\left(1+ \frac{a+b+c}{\sqrt[3]{abc}}\right)$.
94091
In $ \triangle ABC$ show that $ 1 \lt \cos A + \cos B + \cos C \le \frac 32$
135365
If $x, y, z$ are the side lengths of a triangle, prove that $x^2 + y^2 + z^2 < 2(xy + yz + xz)$
90283
Proof that $3 \mid \left( a^2+b^2 \right)$ iff $3 \mid \gcd \left( a,b\right)$
104217
Alternative triangle inequality proof
135543
Proof of Angles going beyond 90 degrees in Trigonometry
62126
Constructing a triangle given 2 sides and the inscribed circle's radius
86753
All right angles are equal to each other
16866
How to Prove $a^3 \cos (B-C) + b^3 \cos (C-A)+ c^3 \cos (A-B)=3abc$?
112740
Prove the triangle is equilateral given that a quadrilateral related to its circumcircle is a kite
120444
Trigonometric Triangle Equality
111003
Prove that if $A\triangle B = C\triangle B$, then $A = C$
41105
Finding the perimeter of a right triangle with area given
19940
How to show that $A^3+B^3+C^3 - 3ABC = (A+B+C)(A+B\omega+C\omega^2)(A+B\omega^2+C\omega)$ indirectly?
111903
An inequality for sides of a triangle