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Pentagrammic crossed-antiprism

Pentagrammic crossed-antiprism is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pentagrammic crossed-antiprism rather than just read about it. In short: In geometry, the pentagrammic crossed-antiprism is one in an infinite set of nonconvex antiprisms formed by triangle sides and two regular star polygon caps, in this case two pentagrams. It differs from the pentagrammic antiprism by having triangular lateral faces which intersect (or "cross") the antiprism's axis of symmetry; in other words, for each lateral face, one of the triangle's vertices is on the opposite si…

Pentagrammic crossed-antiprism — main illustration
Pentagrammic crossed-antiprism — illustration

Key takeaways

  • Pentagrammic crossed-antiprism belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Pentagrammic crossed-antiprism to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Pentagrammic crossed-antiprism from memory before moving on to harder problems.

Reference excerpt

In geometry, the pentagrammic crossed-antiprism is one in an infinite set of nonconvex antiprisms formed by triangle sides and two regular star polygon caps, in this case two pentagrams. It differs from the pentagrammic antiprism by having triangular lateral faces which intersect (or "cross") the antiprism's axis of symmetry; in other words, for each lateral face, one of the triangle's vertices is on the opposite side of the axis of symmetry from the other two. This polyhedron is identified with the indexed name U80 as a uniform polyhedron.

The pentagrammic crossed-antiprism may be inscribed within an icosahedron, and has ten triangular faces in common with the great icosahedron. It has the same vertex arrangement as the pentagonal antiprism. In fact, it may be considered as a parabidiminished great icosahedron.

See also Prismatic uniform polyhedron

External links Weisstein, Eric W. "Pentagrammic crossed antiprism". MathWorld. http://www.mathconsult.ch/showroom/unipoly/80.html http://bulatov.org/polyhedra/uniform/u05.html https://web.archive.org/web/20050313234519/http://www.math.technion.ac.il/~rl/kaleido/data/05.html

Illustrations

Pentagrammic crossed-antiprism illustration
Pentagrammic crossed-antiprism illustration
Pentagrammic crossed-antiprism: 3D model of a (uniform) pentagrammic crossed-antiprism
3D model of a (uniform) pentagrammic crossed-antiprism
Pentagrammic crossed-antiprism illustration
Pentagrammic crossed-antiprism illustration

Worked examples

Example 1 — a first encounter with Pentagrammic crossed-antiprism

Start with the simplest possible case. Write down what Pentagrammic crossed-antiprism claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pentagrammic crossed-antiprism before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pentagrammic crossed-antiprism ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pentagrammic crossed-antiprism

In research
Pentagrammic crossed-antiprism appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Pentagrammic crossed-antiprism in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Pentagrammic crossed-antiprism is common in secondary-school and first-year university syllabi. It links to neighbouring topics Polyhedron stubs, Prismatoid polyhedra, so understanding it makes those chapters shorter.
In everyday life
Look for Pentagrammic crossed-antiprism outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Pentagrammic crossed-antiprism in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Pentagrammic crossed-antiprism means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Pentagrammic crossed-antiprism out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pentagrammic crossed-antiprism in simple terms?

In geometry, the pentagrammic crossed-antiprism is one in an infinite set of nonconvex antiprisms formed by triangle sides and two regular star polygon caps, in this case two pentagrams. It differs from the pentagrammic antiprism by having triangular lateral faces which intersect (or "cross") the a…

Why does Pentagrammic crossed-antiprism matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pentagrammic crossed-antiprism?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pentagrammic crossed-antiprism.

Tags

  • Polyhedron stubs
  • Prismatoid polyhedra

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