A triangle is a three-sided figure. One property of triangles is that all three angles add up to 180 degrees. The longest side is opposite the largest angle, and the shortest side is opposite the smallest angle.
Scalene Triangle.A scalene triangle has three sides of unequal length. All three angles are also unequal.
Isosceles Triangle.A triangle with two sides of equal length and a third side that is either longer or shorter than the other two. Because two sides are equal, the angles opposite these sides are also equal.
Equilateral Triangle.A triangle with three equal sides and three equal angles. Also called an equiangular triangle, each of the angles is 60 degrees.
Obtuse Triangle. A triangle that has one angle with a measure greater than 90 degrees, aka an obtuse angle. The other two angles are necessarily less than 90 degrees.
Right Triangle. A triangle with one angle that is exactly 90 degrees, aka a right angle. The other two angles add up to 90 degrees.
Acute Triangle. A triangle whose three angles are all less than 90 degrees, aka acute angles.