Compute the decimal expansion of , where is the number of consecutive correct digits immediately following the decimal point in your answer.
Solution
For this problem, it is useful to know the following square root algorithm that allows for digit-by-digit extraction of for each two decimal places of . We will illustrate how to extract the second digit after the decimal point of and d be the next decimal digit. Then d should be the largest digit such that (1.7+0.01 , which in this case we will treat as (1.7+0.01 d)^{2}<3.14152.89+0.034 d+0.0001 d^{2}< 3.1415, from which we get the value of d, since the term is negligible. Indeed, 7 is the largest such digit, and so is the second digit of Because we are constantly subtracting the square of our extracted answer so far, we can record the difference in a manner similar to long division, which yields a quick method of extracting square roots by hand.