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My soulver app on iphone says 9 - answer = 1.162985x10^-97 wow. That's basically infinite precision.

But then excel gives a compartively horrible result 8.99999999983268000 (maybe all the casting to and fro degrees and radians makes it worse?)

And python on the same machine, similar: degrees(asin(degrees(acos(degrees(atan(tan(radians(cos(radians(sin(radians(9)))))))))))) = 8.99999999983257

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My android calculator app gives me 9.00000... and lets me scroll through the decimal expansion, it's zeros at least to 1000 places, so presumably the calculator's answer is exactly 9.

I wonder if our calculator apps are doing some symbolic computations? Or just have >>64 bit precision (which I presume is the default for excel/python)?

The Android calculator is indeed doing unbounded precision calculations[0.999999999999]. It was developed by Hans-J Boehm, also known for the Boehm-Weiser conservative garbage collector.

[0.999999999999]: https://cacm.acm.org/magazines/2017/8/219594-small-data-comp...

The Android calculator really has no reason to be so excellent, but I greatly appreciate it.

Everything should do unbounded precision. The results are much more human-friendly. And if you're not building a calculator app for humans, who are you building it for?

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