If a side is labelled, you know its length. That will only happen in an equilateral triangle.īy definition of an equilateral triangle, you already know all three sides are congruent and all three angles are 60 °. In an equilateral triangle, like △ S U N below, each height is the line segment that splits a side in half and is also an angle bisector of the opposite angle. A triangle's height is the length of a perpendicular line segment originating on a side and intersecting the opposite angle. Every triangle has three heights, or altitudes, because every triangle has three sides.
