An infinite series of similar triangles converge to a point C . If
. Denote
as the sum of all the vertical segments:
Find the value of .
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Let ∠ A E B = ∠ E B D = . . . = θ . We note that: A E cos θ = E B and E B sin θ = E D .
⇒ E B sin θ A E cos θ sin θ 1 6 cos θ sin θ 2 cos θ sin θ sin 2 θ ⇒ θ = E D = E D = 8 = 1 = 1 = 4 5 ∘
Therefore, the similar triangles are isosceles triangles with the horizontal side same length with vertical side. And the vertical height is half of that of the previous one. Therefore, we have:
x = 1 6 + 8 + 4 + . . . = 1 6 ( 1 + 2 1 + 4 1 + . . . )
= 1 6 n = 0 ∑ ∞ ( 2 1 ) n = 1 − 2 1 1 6 = 3 2