Exercise 7.3.3 (Some infinite continued fractions)

Evaluate the infinite continued fractions:

(a) 2 , 2 , 2 , 2 , ; (b) 1 , 2 , 1 , 2 , 1 , 2 , ;
(c) 2 , 1 , 2 , 1 , 2 , 1 , ; (d) 1 , 3 , 1 , 2 , 1 , 2 , 1 , 2 , .

Answers

Proof. Only with Sagemath this time!

age: cf = continued_fraction([(),(2,)]); cf
[(2)*]
sage: cf.value()
sqrt2 + 1
sage: cf = continued_fraction([(),(1,2)]); cf
[(1, 2)*]
sage: cf.value()
1/2*sqrt3 + 1/2
sage: cf = continued_fraction([(),(2,1)]); cf
[(2, 1)*]
sage: cf.value()
sqrt3 + 1
sage: cf = continued_fraction([(1,3),(1,2)]); cf
[1; 3, (1, 2)*]
sage: cf.value()
-sqrt3 + 3

This gives

2 , 2 , 2 , 2 , = 1 + 2 , 1 , 2 , 1 , 2 , 1 , 2 , = 1 + 3 2 , 2 , 1 , 2 , 1 , 2 , 1 , = 1 + 3 1 , 3 , 1 , 2 , 1 , 2 , 1 , 2 , = 3 3 .
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2025-07-24 10:03
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