# New Reuleaux Triangle Magic | Summary and Q&A

159.7K views
February 16, 2019
by
Mathologer
New Reuleaux Triangle Magic

## TL;DR

Shapes of constant width, such as the Reuleaux triangle, have fascinating properties and applications, including creating a unique ferris wheel and solving common engineering challenges.

## Key Insights

• 🎡 Shapes of constant width, such as the Reuleaux triangle and regular polygons, have the same width in all directions, making them ideal for creating structures like a ferris wheel.
• 👷 These shapes can be easily constructed by drawing circles centered around the corners of certain polygons.
• 🎰 Shapes of constant width have practical applications, including creating coins that are cost-effective and can be easily identified by machines.
• 🕳️ Manhole covers of constant width prevent accidents by ensuring they cannot fall into the corresponding holes.
• 🍧 Shapes of constant width have unique properties, such as having the same perimeter as a circle according to Barbier's theorem.
• 🤗 Exploring the properties of shapes of constant width opens up possibilities for innovative and creative designs, such as the creation of a smooth car ride using non-circular rollers.
• 😥 The alignment of contact points between shapes of constant width allows for interesting and engaging dance games and movements.

## Transcript

Welcome to another Mathologer video. This is a special mathematical ferris wheel, a geometrical gem that has only recently been discovered. Notice how the cabins of the ferris wheel always just touch and brush along their neighbours. Pretty mesmerizing an impossible looking isn't it? Here's another example of the same kind of mathematical magic. Th... Read More

### Q: What is the defining property of shapes of constant width?

Shapes of constant width have the same width no matter which direction they are measured, making them unique and different from regular polygons or circles.

### Q: How can shapes of constant width be applied in practical situations, such as coins and manhole covers?

Non-circular coins of constant width are cheaper to produce and can be easily identified by coin-operated machines. Manhole covers of constant width, like the Reuleaux triangle, ensure safety by never falling into smaller holes.

### Q: What challenges arise when constructing shapes of constant width with even-sided polygons?

When constructing shapes of constant width with an even-sided polygon, the resulting shape will not have a constant width as it will be wider in some directions and narrower in others.

### Q: What is Barbier's theorem, and how does it relate to shapes of constant width?

Barbier's theorem states that all shapes of constant width have the same perimeter as a circle, which is a surprising and fascinating property of these shapes.

## Summary & Key Takeaways

• Shapes of constant width, like the Reuleaux triangle, have the same width no matter which direction they are measured, making them perfect for creating mesmerizing structures like a ferris wheel.

• These shapes can be constructed by drawing circles centered around the corners of certain polygons, such as equilateral triangles or regular pentagons.

• Shapes of constant width have practical applications, such as creating coins that are easier and cheaper to produce, and ensuring manhole covers cannot fall into their corresponding holes.