A triangle is the shape with the fewest number of sides, and thus the most acute or “closed” internal angles, of any shape. 2-sided shapes dont exist, and squares/rectangles have a wider internal angle.
A shapes “strength” is derived from how much force is needed to “bend” each angle open. The more closed the angle starts, the more force it takes to “open” the angle.
Triangles have the most “closed” angles. Squares are number 2, pentagons number 3, etc.
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