Crossword Classic 7

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Across
  1. 2. Formed by an intersection between two disks of the same radius
  2. 5. Has an outer atmosphere containing 3.25% helium by volume
  3. 7. Is composed of 20 intersecting triangular faces, having five triangles meeting at each vertex in a pentagrammic sequence
  4. 8. The lightest element in group 15 of the periodic table
  5. 9. = 2.71828
  6. 10. Radiation present in sunlight
Down
  1. 1. A polyhedron that has regular polygons as faces and is vertex-transitive
  2. 3. What cot stands for
  3. 4. A sentence containing every letter in the language
  4. 6. A polygon containing 1 billion sides
  5. 11. Has a dominant wavelength of approximately 625–740 nanometres