The three interior angles of a triangle always add up to 180 degrees, which is one of the identifying characteristics of a triangle. Each shape has properties that are unique to that specific figure. Other identifying properties are that the exterior angles of a trangle always add up to 360 degrees and that a triangle always has three sides.
Many combinations of angle can be used to meet the 180 degree requirement. An obtuse triangle has one obtuse angle (an angle that measures between 90 and 180 degrees) and two acute angles (angles that measure less than 90 degrees). A right angle triangle has a single 90 degree angle and two acute angles. The acute triangle is composed of three acute angles.