Let .
In right with , and are tangent to the two inscribed unit semicircles at and respectively.
Extend the above diagram to congruent unit circles as follows:
Draw another unit semicircle through C and construct the tangent from B and mark the intersection with the extended line AC and continue this process for the unit semicircles.
(1) Find a formula for the area of the right triangle formed which contains the unit semicircles.
(2) Using and write a program to compute the area of .
Below is a diagram for the area of
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Let m > 1 .
△ A B D ∼ △ E F D ⟹ m = y 1 B D ⟹ B D = m y 1
Using the Pythagorean theorem on △ A B D ⟹ m 2 y 1 2 = m 2 + ( 1 + y 1 ) 2 ⟹
( m 2 − 1 ) y 1 2 − 2 y 1 − ( m 2 + 1 ) = 0 ⟹ y 1 = m 2 − 1 m 2 + 1 ⟹
d 1 = A D = m 2 − 1 2 m 2 ⟹ A 1 = m 2 − 1 m 3 .
d 1 = m 2 − 1 2 m 2 ⟹ m 2 + ( d 1 + 1 + y 2 2 ) 2 = m 2 y 2 2 ⟹
( m 2 − 1 ) y 2 2 − 2 ( d 1 + 1 ) y 2 − ( m 2 + ( d 1 + 1 ) 2 ) = 0 ⟹
y 2 = m 2 − 1 d 1 + 1 + m ( d 1 + 1 ) 2 + m 2 − 1
d 2 = d 1 + 1 + y 2 = m 2 − 1 m ( ( d 1 + 1 ) m + ( d 1 + 1 ) 2 + m 2 − 1 )
Similarly m 2 + ( d 2 + 1 + y 3 ) 2 = m 2 y 3 2 ⟹
( m 2 − 1 ) y 3 2 − 2 ( d 2 + 1 ) y 3 − ( m 2 + ( d 2 + 1 ) 2 ) = 0 ⟹
y 3 = m 2 − 1 d 2 + 1 + m ( d 2 + 1 ) 2 + m 2 − 1 ⟹
d 3 = d 2 + 1 + y 3 = d 2 + 1 + y 3 = m 2 − 1 m ( ( d 2 + 1 ) m + ( d 2 + 1 ) 2 + m 2 − 1 )
In General using A 1 = m 2 − 1 m 3
Let d 1 = m 2 − 1 2 m 2
and for n ≥ 1 define:
d n + 1 = m 2 − 1 m ( ( d n + 1 ) m + ( d n + 1 ) 2 + m 2 − 1 ) and A n + 1 = 2 m d n + 1
or if you prefer d n + 1 = m 2 − 1 m ( ( d n + 1 ) m + d n 2 + 2 d n + m 2 ) and A n + 1 = 2 m d n + 1
Using the above recursive formula with m = 2 the program below computes A 1 0 using python:
0
⟹ A 1 0 = 2 4 7 3 . 0 0 4 9 3 6 8 0 9 9 9 .