Is it possible to prove that a triangle has 180 degrees, without using parallel line properties?
117431
Are the proofs for the properties of parallel lines, and that a triangle has 180 degrees, inherently tautological?
96065
Question about sines of angles in an acute triangle
118577
Fallacious proof involving trigonometry
52122
Find an angle of an isosceles triangle
27954
Prove triangle inequality using the properties of absolute value
40596
Proving a relation between inradius ,circumradius and exradii in a triangle
83493
Map an arbitrary triangle to the unit square
67383
Prove that $G'$ is not planar.
57195
Plotting layer given with Longitudes [0 360] to [-180 180]?
131736
Proving a triangle with different edge colors exists in a graph.
68869
How to show that the triangle is equilateral triangle?
112740
Prove the triangle is equilateral given that a quadrilateral related to its circumcircle is a kite
73029
If a,b,c are sides of a triangle, prove: $ \sqrt{a+b-c} + \sqrt{b+c-a} + \sqrt{c+a-b} \le \sqrt{a} + \sqrt{b} + \sqrt{c} $
56609
Do Zero degree angles exist?
104217
Alternative triangle inequality proof
84334
How to prove the Pythagoras theorem using vectors
21745
Proof of Heron's Formula for the area of a triangle