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cthulhu944 t1_j242d0n wrote

There is a mathematical concept called a taylor series that can be used to compute things like irrational roots. It is way beyond the scope of eli5. The basic concept is that you can repeatedly call this function and each iteration gets you closer to the real value.

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FearlessFaa t1_j2455m7 wrote

Although partial sums of Taylor series use basic arithmetic operations so one could post an answer that calculates partial sums of Taylor series. We could then compare that with the average method described by other answers.

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cthulhu944 t1_j24ssd7 wrote

You can use the average method to compute a square root, but the question was how a calculator computes it. That is definitely done by using a taylor series.

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FearlessFaa t1_j24vms7 wrote

I think to the question it is unrelevant how physical calculators do it since physical calculators are not used much anymore. We are interested how to calculate square root i.e. different algorithms (=methods) used to calculate square root. It’s unrelevant what specific method calculators use.

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cthulhu944 t1_j2a8kps wrote

Maybe I should clarify my point then. Taylor series is the way pretty much every system (calculator, computer, cell phone, etc) computes a square root. You can look into the c stadard library and find the the sqrt funtion is implemented with a taylor series. This is because it is computationally efficient and provides a predictable level of accuracy. The estimation algorithm that every other person on this thread has mentioned is really only used by people wanting to do a manual computation, or as an exercise in an introductory computer science class.

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