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  2. Golden rhombus - Wikipedia

    en.wikipedia.org/wiki/Golden_rhombus

    By using the area formula of the general rhombus in terms of its diagonal lengths and : The area of the golden rhombus in terms of its diagonal length d {\displaystyle d} is: [ 6 ] A = ( φ d ) ⋅ d 2 = φ 2 d 2 = 1 + 5 4 d 2 ≈ 0.80902 d 2 . {\displaystyle A={{(\varphi d)\cdot d} \over 2}={{\varphi } \over 2}~d^{2}={{1+{\sqrt {5}}} \over 4 ...

  3. Orthodiagonal quadrilateral - Wikipedia

    en.wikipedia.org/wiki/Orthodiagonal_quadrilateral

    The area K of an orthodiagonal quadrilateral equals one half the product of the lengths of the diagonals p and q: [8] K = p q 2 . {\displaystyle K={\frac {pq}{2}}.} Conversely, any convex quadrilateral where the area can be calculated with this formula must be orthodiagonal. [ 6 ]

  4. Rhombus - Wikipedia

    en.wikipedia.org/wiki/Rhombus

    A rhombus therefore has all of the properties of a parallelogram: for example, opposite sides are parallel; adjacent angles are supplementary; the two diagonals bisect one another; any line through the midpoint bisects the area; and the sum of the squares of the sides equals the sum of the squares of the diagonals (the parallelogram law).

  5. Golden ratio - Wikipedia

    en.wikipedia.org/wiki/Golden_ratio

    The rhombic Penrose tiling contains two types of rhombus, a thin rhombus with angles of ⁠ ⁠ and ⁠ ⁠, and a thick rhombus with angles of ⁠ ⁠ and ⁠ ⁠. All side lengths are equal, but the ratio of the length of sides to the short diagonal in the thin rhombus equals ⁠ 1 : φ {\displaystyle 1\mathbin {:} \varphi } ⁠ , as does the ...

  6. Rhombic triacontahedron - Wikipedia

    en.wikipedia.org/wiki/Rhombic_triacontahedron

    The ratio of the long diagonal to the short diagonal of each face is exactly equal to the golden ratio, φ, so that the acute angles on each face measure 2 arctan(⁠ 1 / φ ⁠) = arctan(2), or approximately 63.43°. A rhombus so obtained is called a golden rhombus.

  7. Varignon's theorem - Wikipedia

    en.wikipedia.org/wiki/Varignon's_theorem

    An arbitrary quadrilateral and its diagonals. Bases of similar triangles are parallel to the blue diagonal. Ditto for the red diagonal. The base pairs form a parallelogram with half the area of the quadrilateral, A q, as the sum of the areas of the four large triangles, A l is 2 A q (each of the two pairs reconstructs the quadrilateral) while that of the small triangles, A s is a quarter of A ...

  8. Tangential quadrilateral - Wikipedia

    en.wikipedia.org/wiki/Tangential_quadrilateral

    If the incircle is tangent to the sides AB, BC, CD, DA at T 1, T 2, T 3, T 4 respectively, and if N 1, N 2, N 3, N 4 are the isotomic conjugates of these points with respect to the corresponding sides (that is, AT 1 = BN 1 and so on), then the Nagel point of the tangential quadrilateral is defined as the intersection of the lines N 1 N 3 and N ...

  9. Rhombic dodecahedron - Wikipedia

    en.wikipedia.org/wiki/Rhombic_dodecahedron

    For example, with 4 square faces, and 60-degree rhombic faces, and D 4h dihedral symmetry, order 16. It can be seen as a cuboctahedron with square pyramids attached on the top and bottom. In 1960, Stanko Bilinski discovered a second rhombic dodecahedron with 12 congruent rhombus faces, the Bilinski dodecahedron. It has the same topology but ...