CK-12 Foundation
Comparing Triangle Angles and Sides: Lesson
Use the opposite to organize angles or sides. The video provides the relationship of angle measures based on the lengths of sides in a triangle and its converse. Using two triangles, the segment of a larger playlist on geometry shows the...
CK-12 Foundation
Triangle Inequality Theorem: Lesson
Can any three lengths make a triangle? One of the videos in a playlist on basic geometry introduces the Triangle Inequality Theorem. Using three given lengths, the presentation illustrates the restrictions on lengths of any side of a...
PBS
5 Unusual Proofs
A fast-paced video offers examples of proof techniques. It covers logic, bijections, applying previous math results, mathematical induction, and proofs with pictures.