Definition of Terms, ContinuedTrianglesA triangle is a plane figure bound by three straight sides, which form threeinterior angles. The top of the triangle is the vertex. The height of a triangleis referred to as the altitude. The bottom of a triangle is its base. The sumof the three interior angles is always 180°. When all sides and all interiorangles (60°) are equal, the triangle is referred to as an equilateral triangle.When two sides and two angles are equal, the triangle is an isoscelestriangle. A scalene triangle does not have any equal sides or angles. A righttriangle has one angle equal to 90° and the long side opposing that angle iscalled the hypotenuse.Figure 2-4 shows triangles.Figure 2-4.—Triangles.Continued on next page2-6