Yes, the definition of a polygon is any closed figure with straight sides.
A right angle triangle
A 3 side polygon is a TRIANGLE.
triangle
Any polygon can have just one right angle, from a right angled triangle upwards.
No. A three-sided polygon is, by definition, a triangle.
A triangle
Any polygon can have a right angle. A right angled triangle is an example.
it can be a triangle that is right, acute, or obtuse
No.
right triangle
A right angle triangle
An isosceles right angled triangle.
No, but an equilateral triangle is a regular polygon with 3 equal sides and 3 equal angles.
A polygon can be any one of them.
equilateral triangle
A triangle.
Any polygon can have at least one right angled - for example a right angled triangle. An example of an irregular polygon with only right angles is a rectangle.