If all sides different scalene .
if two sides equal isosceles .
if all sides equal equilateral .
ıf all angles acute, acute triangle .
One angle right or obtuse, then right or obtuse triangle.
Some include equilateral but not generally accepted.
Vertices are not considered as parts, they are dimensionless
Half of a square is not necessarily a triangle .
Triangle inequality is pretty important .
Since the sum of inner angles of a triangle is 180 degrees, ... .
Isosceles triangles do have two of their interior angles equal.
In isosceles triangles the inequal angle is usually considered as the vertex angle. The side opposite vertex angle is the base and base angles
are equal .
In right triangles the sides including the right angle are called legs and the (longest) side opposite the right angle is called
The ∠B is included by the sides AB and BC .
The side AB is included by ∠A and ∠B .
When a side of a triangle is also a side of another triangle we say the side is common .