Inequalities for One Triangle Section 6-4 Inequalities for One Triangle

Theorem 6-2 If one side of a triangle is longer than a second side, then the angle opposite the first side is larger than the angle opposite the second side.

Example: N D A 6 8 10

Theorem 6-3 If one angle of a triangle is larger than a second angle, then the side opposite the first angle is longer than the side opposite the second angle.

Example: C A T CT < TA < CA

Corollary 1 The perpendicular segment from a point to a line is the shortest segment from the point to the line.

Corollary 2 The perpendicular segment from a point to a plane is the shortest segment from the point to the plane.

Theorem 6-4: The Triangle Inequality Theorem The sum of the lengths of any two sides of a triangle is greater than the length of the third side.

Example #1: Is it possible for a triangle to have sides with the lengths as indicated? a.) 6, 6, 5 b.) 3, 4, 8 c.) 2.5, 4.1, 5.0 Yes No Yes

Example #2: The lengths of two sides of a triangle are 8 and 13. Then, the length of the third side must be greater than ______ but less than ______. 5 21