Triangle
You have described an equilateral triangle.
An equilateral triangle
Triangle
A triangle
Polygon
It is an equilateral triangle
An equilateral triangle
You have described an equilateral triangle.
An equilateral triangle
It's probably a triangle. A triangle has three sides and three angles.
Polygon
Triangle
A triangle
Polygon
The sum of the interior angles of a polygon with n sides is (n-2)*180 degrees. So n = 3 gives (3-1)*180 = 180 degrees. Incidentally, a polygon with three sides (a triangle) must be convex.
No REGULAR polygon can have three right angles in it. Any polygon with five or more sides CAN have three right angles, as long as it's not regular.
A three-sided polygon is a triangle. The angles in a triangle add up to 180 degrees.