Triangle Inequality

The triangle inequality states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side.

Triangle inequality is a high school-level concept that would be first encountered in a geometry course covering plane geometry. It is listed in the California State Standards for Geometry.

Prerequisites

Triangle:

A triangle is a three-sided (and three-angled) polygon.

Classroom Articles on Plane Geometry

	Acute Angle	Hypotenuse
	Altitude	Midpoint
	Angle	Obtuse Angle
	Area	Parallel
	Circle	Perimeter
	Circumference	Perpendicular
	Collinear	Pi
	Complementary Angles	Plane Geometry
	Diameter	Point
	Geometric Construction	Radius
	Golden Ratio	Supplementary Angles
	Golden Rectangle

Classroom Articles on Geometry (Up to High School Level)

	Cone	Octahedron
	Congruent	Parallelogram
	Convex Hull	Pentagon
	Cross Section	Platonic Solid
	Cube	Polygon
	Cylinder	Polyhedron
	Decagon	Polytope
	Dodecagon	Prism
	Dodecahedron	Pyramid
	Equilateral Triangle	Quadrilateral
	Geometry	Rectangle
	Hendecagon	Regular Polygon
	Heptagon	Right Triangle
	Hexagon	Similar
	High-Dimensional Solid	Solid Geometry
	Hypercube	Sphere
	Hyperplane	Square
	Hypersphere	Surface
	Icosahedron	Surface Area
	Isosceles Triangle	Tetrahedron
	Linear Function	Trapezoid
	Nonagon	Volume
	Octagon