I suggest you give some thought to the meaning and derivation of the word "TRI-angle"
Three
In plane geometry at least two angles must be acute in a triangle.
Triangle
The fewest number of right angles in a triangle is zero.
If you mean EQUAL sides and angles, than an equilateral triangle.
A triangle
A triangle.
Triangle is plane with three sides and three angles. The sum of its inside angles is equal to 180 degrees.
All the angles in ANY triangle [on a plane surface] add up to 180 degrees.
They are possible - unlike plane triangles in which all of the angles are right angles, obtuse or larger.
Not on a plane surface.
One example would be a triangle. A triangle has three angles.
No - not a plane triangle. The angles of a regular triangle must be equal. So an obtuse triangle, if regular, would have three obtuse angles. The sum of the angles would then be greater than 3*90 = 270 degrees. But the sum of angles of a triangle must be 180 degrees.