Extend the diagram above to an infinite number of inscribed hexagons.
Let H j be the j t h regular hexagon and H j + 1 be inscribed in H j , where each vertex of H j + 1 touches each midpoint of each side of H j .
For j ≥ 0 let A j be the area of j t h hexagon.
If A = ∑ j = 0 ∞ A j , find A 0 A ..
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Let x 0 be a side of the initial hexagon ⟹ the height h 0 of the initial hexagon is h 0 = 2 3 x 0 = x 1
⟹ h 1 = 2 3 h 0 = ( 2 3 ) 2 x 0 = x 2 ⟹ h 2 = 2 3 h 1 = ( 2 3 ) 3 x 0 = x 3 and h j − 1 = ( 2 3 ) j x 0 = x j ⟹ h j = ( 2 3 ) j + 1 x 0 .
∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ x 0 2 3 x 0 ( 2 3 ) 2 x 0 . . . ( 2 3 ) j x 0 2 3 x 0 ( 2 3 ) 2 x 0 ( 2 3 ) 3 x 0 . . . ( 2 3 ) j + 1 x 0 ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣ ∣
⟹ A j = 6 ( 2 1 ) ( 2 3 ) j ( 2 3 ) j + 1 x 0 2 = 3 ( 2 3 ) 2 j + 1 x 0 2 = 2 3 3 x 0 2 ( 4 3 ) j = ( 4 3 ) j A 0 ⟹
A = ∑ j = 0 ∞ A j = A 0 ∑ j = 0 ∞ ( 4 3 ) j = 4 A 0 ⟹ A 0 A = 4 .
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W L O G l e t S o = 1 b e t h e s i d e o f t h e f i r s t h e x a g o n . . A h e x a g o n i s f o r m e d b y s i x e q u i l a t e r a l Δ s , w i t h s i d e = S . ⟹ r a t i o o f c o r r e s p o n d i n g e q u i l a t e r a l Δ s , w i l l b e t h e s a m e a s t h e o n e r e q u i r e d . A s s e e n f r o m t h e s k e t c h t h e s i d e r a t i o s a r e 2 3 . ⟹ a r e a r a t i o s , A 1 / A o = ( 2 3 ) 2 = 4 3 . ∴ w e h a v e a r e a s u m a s : A = 4 3 ∗ { 1 2 + 4 3 + ( 4 3 ) 2 + ( 4 3 ) 3 . . . } = 4 3 ∗ n = 0 ∑ ∞ ( 4 3 ) n . T h i s i s a G . P . s o s u m 1 − r a = 1 − 4 3 1 = 4 . S o A o A = 4 3 ∗ 1 4 3 ∗ 4 = 4 .