Approximate pi to 24 digits via keyboard

[Werner]

Another way of seeing how many pi digits are used internally is to calculate the sine (in radians) of 10^10, 10^20, 10^30 etc and comparing with the true value, obtained with WolframAlpha:

Code:


SINRAD    WA                     HP42S                 HP41
10^10    -0.4875060250875...    -0.487506025088        -0.4880805565
10^20    -0.6452512852657...    -0.645251285266
10^30    -0.0901169019121...    -0.0910311968368

Easy to see that the results indicate 31 digits for the 42S and 13 for the 41C.