Video narration
Can the same three fixed-length sticks make two different triangles? Lay three sticks edge to edge and their ends meet: you have a triangle. Make another from sticks the same lengths. Match each side of the first triangle with its equal-length partner in the second: one side, then the next, then the third. Two matched sticks can still leave the shape free to shift. But the last stick has a fixed length too. That third length locks it. SSS means side-side-side: all three corresponding sides match in length. When they do, the triangles are congruent, meaning they have the same size and shape. One triangle can be turned around or flipped, so it looks different in position, but the same three sticks still fit. So, can those three lengths make congruent triangles? Yes-even when one is flipped.