A hemi-icosahedron is an abstract regular polyhedron, containing half the faces of a regular icosahedron. It can be realized as a projective polyhedron (a tessellation of the real projective plane by 10 triangles), which can be visualized by constructing the projective plane as a hemisphere where opposite points along the boundary are connected and dividing the hemisphere into three equal parts. (Wikipedia).
How to Construct an Icosahedron
How the greeks constructed the icosahedron. Source: Euclids Elements Book 13, Proposition 16. In geometry, a regular icosahedron is a convex polyhedron with 20 faces, 30 edges and 12 vertices. It is one of the five Platonic solids, and the one with the most faces. https://www.etsy.com/lis
From playlist Platonic Solids
The remarkable Platonic solids II: symmetry | Universal Hyperbolic Geometry 48 | NJ Wildberger
We look at the symmetries of the Platonic solids, starting here with rigid motions, which are essentially rotations about fixed axes. We use the normalization of angle whereby one full turn has the value one, and also connect the number of rigid motions with the number of directed edges.
From playlist Universal Hyperbolic Geometry
The remarkable Platonic solids I | Universal Hyperbolic Geometry 47 | NJ Wildberger
The Platonic solids have fascinated mankind for thousands of years. These regular solids embody some kind of fundamental symmetry and their analogues in the hyperbolic setting will open up a whole new domain of discourse. Here we give an introduction to these fascinating objects: the tetra
From playlist Universal Hyperbolic Geometry
This shows a 3d print of a mathematical sculpture I produced using shapeways.com. This model is available at http://shpws.me/q0PF.
From playlist 3D printing
Canonical structures inside the Platonic solids III | Universal Hyperbolic Geometry 51
The dodecahedron is surely one of the truly great mathematical objects---revered by the ancient Greeks, Kepler, and many mathematicians since. Its symmetries are particularly rich, and in this video we look at how to see the five-fold and six-fold symmetries of this object via internal str
From playlist Universal Hyperbolic Geometry
How to Construct a Dodecahedron
How the greeks constructed the Dodecahedron. Euclids Elements Book 13, Proposition 17. In geometry, a dodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagons as faces, which is a Platonic solid. A regular dode
From playlist Platonic Solids
Rade Zivaljevic (6/27/17) Bedlewo: Topological methods in discrete geometry; new developments
Some new applications of the configurations space/test map scheme can be found in Chapter 21 of the latest (third) edition of the Handbook of Discrete and Computational Geometry [2]. In this lecture we focus on some of the new developments which, due to the limitations of space, may have b
From playlist Applied Topology in Będlewo 2017
AlgTop8: Polyhedra and Euler's formula
We investigate the five Platonic solids: tetrahedron, cube, octohedron, icosahedron and dodecahedron. Euler's formula relates the number of vertices, edges and faces. We give a proof using a triangulation argument and the flow down a sphere. This is the eighth lecture in this beginner's
From playlist Algebraic Topology: a beginner's course - N J Wildberger
What Are Allotropes of Metalloids and Metals | Properties of Matter | Chemistry | FuseSchool
What Are Allotropes of Metalloids and Metals Learn the basics about allotropes of metalloids and metals, as a part of the overall properties of matter topic. An allotrope is basically a different form of the same element, each with distinct physical and chemical properties. For example
From playlist CHEMISTRY
Henry Segerman shows us shadows (and dust) from the fourth dimension! More links & stuff in full description below ↓↓↓ Dr Segerman is an assistant professor in the Department of Mathematics at Oklahoma State University. More Numberphile with him: http://bit.ly/Segerman_Videos Polytopes i
From playlist Henry Segerman on Numberphile
Post 1462H / Hemmi 159 and a slide rule conspiracy!
I describe the interesting Post 1462H slide rule and its predecessor/successor. I present the theory that these slide rules inspired a certain model popular in Europe.
From playlist All Slide Rule Videos
Frankenrule: the Hemmi 258ab slide rule
Witness an unholy combination of slide rules: the Hemmi 259 and the Versalog II.
From playlist All Slide Rule Videos
I describe one of my favorite scale sets: the Hemmi 260 scale set.
From playlist All Slide Rule Videos
Pawn Stars: 1966 Dodge Charger with Hemi Engine (Season 14) | History
Rick takes a spin in a rare '66 Dodge Charger with a Hemi engine that might be 1 of 85 produced by NASCAR in this clip from "The Greatest Pawn on Earth!" #PawnStars Subscribe for more from Pawn Stars: http://po.st/SubscribeToPawnStars Watch more Pawn Stars on YouTube in this playlist: htt
From playlist Pawn Stars: Official Series Playlist | New Episodes Wednesdays at 8/7c | History
Hemmi 260 Layout 2/2: Runners-Up Club
I describe two slide rules with layouts similar to the Hemmi 260: The Graphoplex 690a and the Aristo 970.
From playlist All Slide Rule Videos
Slide Rule Roundup -- 1955* Duplex Engineering Edition
An overview of some popular engineering slide rules available in the mid '50s. Let me know your favorite below, whether or not it was one of these! * Some slide rules in the roundup were made in later production runs than 1955. Also, the Dietzgen N1733 was not available until 1956. The 17
From playlist All Slide Rule Videos
Canonical structures inside Platonic solids II | Universal Hyperbolic Geometry 50 | NJ Wildberger
The cube and the octahedron are dual solids. Each has contained within it both 2-fold, 3-fold and 4-fold symmetry. In this video we look at how these symmetries are generated in the cube via canonical structures. Along the way we discuss bipartite graphs. This gives us more insight into t
From playlist Universal Hyperbolic Geometry
Hemmi 153 Electrical Engineer's Slide Rule with Gudermannian Scale (1/3: Overview)
First video in a three video series about the Sun Hemmi 153, a slide rule with the unique Gtheta Gudermannian scale and a non-standard trigonometric scale setup.
From playlist All Slide Rule Videos
Using a set of points determine if the figure is a parallelogram using the midpoint formula
👉 Learn how to determine the figure given four points. A quadrilateral is a polygon with four sides. Some of the types of quadrilaterals are: parallelogram, square, rectangle, rhombus, kite, trapezoid, etc. Each of the types of quadrilateral has its properties. Given four points that repr
From playlist Quadrilaterals on a Coordinate Plane
Group theory 27: The icosahedral group
This lecture is part of an online math course on group theory. The lecture is about a few examples of groups, in particular the icosahedral group. In it we see that the icosahedral group is the only simple group of order 60, and show that all larger alternating groups are simple.
From playlist Group theory