In mathematics, the triangle inequality is the theorem stating that for any triangle, the length of a given sie must be less than or equal to the sum of the other two sides but greater than or equal to the difference between the two sides. (In both the less than or equal to and greater than or equal to statements, equality only occurs in the case of a triangle that has a 180° angle and two 0° angles, as shown in the bottom example in the image to the right.) The inequality can be viewed intuitively in either R2 or R3. The figure at the right shows two examples.