Three Sides Make One Triangle
Give three side lengths (5, 6 and 7 cm) and there's only one way to close them into a triangle. Side-side-side is enough to pin a triangle down.
Transcript
[1] [Sides of 5 cm, 6 cm and 7 cm, not yet joined; arrows push the 5 cm and 6 cm sides inward; a nervous face] [2] [The same sides closed into a triangle, smiling]
Use this cartoon
Free for classrooms, worksheets, slides and other non-commercial use under CC BY-NC 4.0, with credit to Ben Orlin.
Cartoon by Ben Orlin, Math with Bad Drawings. https://cartoons.mathwithbaddrawings.com/2018-09-18-three-sides-make-one-triangle/ (CC BY-NC 4.0)