Pentagons sentence example
- In crystallography, the regular or ordinary dodecahedron is an impossible form since the faces cut the axes in irrational ratios; the "pentagonal dodecahedron" of crystallographers has irregular pentagons for faces, while the geometrical solid, on the other hand, has regular ones.
- However, the American mathematician George Birkhoff showed in 1913 that a particular arrangement of four adjacent pentagons is reducible.
- Three pentagons may be placed at a common vertex to form a solid angle, and by forming several such sets and placing them in juxtaposition .a solid is obtained having 12 pentagonal faces, 30 edges, and 20 vertices.
- Square or rectangular wedding cakes look classic with their clean lines, and more unusual shapes, such as hexagons or pentagons, make for beautiful presentations.
- Then move to pentagons (5 sides), hexagons (6 sides), and octagons (8 sides), etc. if it appears that children have mastered the first set of shapes.Advertisement
- The pentagons belong to a dodecahedron, and 20 triangles to an icosahedron; the remaining 60 triangles belong to no regular solid.
- So now we have 6 pentagons in total, half the total to be found going around the ball.
- Second order pentagons are made from six first order pentagons plus five first order triangles.