Triangle Inequality

Videos, worksheets, stories and songs to help Grade 8 students learn about the triangle inequality theorem.



Description of the Triangle Inequality



Triangle Inequality Theorem



Triangle Inequality
The triangle inequality theorem states that the sum of any two sides of a triangle must be greater than the length of the third side. To find a range of values for the third side when given two lengths, write two inequalities: one inequality that assumes the larger value given is the longest side in the triangle and one inequality that assumes that the third side is the longest side in the triangle. Combine the two inequalities for the final answer.

How to determine the triangle side inequalities.



Triangle Side and Angle Inequalities
In any triangle, the largest angle is opposite the largest side (the opposite side of an angle is the side that does not form the angle). The shortest angle is opposite the shortest side. Therefore, the angle measures can be used to list the size order of the sides. The converse is also true: the lengths of the sides can be used to order the relative size of the angles. Triangle side and angle inequalities are important when solving proofs.

How to determine the relationship between the side inequalities and angle inequalities in a triangle.




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