Triples And 3D

Some right triangles come out in tidy whole numbers. These Pythagorean triples are worth recognizing on sight:

• 3, 4, 5
• 5, 12, 13
• 8, 15, 17

The rule also climbs into three dimensions. For a box, the longest diagonal from one corner to the opposite corner is √(a² + b² + c²) — the same idea with one extra term. That's how you check whether a long pole will fit inside a moving truck.