#15 in Drafting tools & drafting kits
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Reddit mentions of hand2mind 85104 Polydron Triangles (Pack of 100)
Sentiment score: 1
Reddit mentions: 1
We found 1 Reddit mentions of hand2mind 85104 Polydron Triangles (Pack of 100). Here are the top ones.
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- Durable plastic shapes of the polypro geometric construction system feature a unique clip hinge
- Hinge allows students to snap the shapes together to easily explore two-dimensional nets and three-dimensional solids; perimeter, volume, vertices, and angles; and Euler's formula
- These polypro triangles are packaged in a set of 100 pieces
Features:
Specs:
| Number of items | 100 |
| Release date | March 2017 |
| Weight | 1.3 Pounds |
This is a physical way of demonstrating one (of many) definition of scalar curvature. Wikipedia has a good formula and explanation. https://en.wikipedia.org/wiki/Scalar_curvature#Direct_geometric_interpretation
Hopefully a more intuitive explanation is the following. Let A(r) denote the area of a circle (the set of all points in the surface at distance r to p) around a point p on the surface. Express A(r) as a Taylor expansion around r = 0. At orders 0 through 3, the series matches the formula one would get in flat space. At fourth order, it stops matching (in flat space the series is just \pi r\^2), and the coefficient of r\^4 is scalar curvature.
What this means is that for surfaces of positive curvature, there is less area than there should be in the plane, so when you flatten it into a plane there's a gap. For surfaces of negative curvature, there is more area than there should be in the plane, so you get a ripple refusing to flatten down. I like to think of a kale leaf.
When I learned this, my prof brought a kale leaf to class. I have a favorite tool for demonstrating this to students: https://www.amazon.com/ETA-hand2mind-85104-Polydron-Triangles/dp/B06XJH14M8