HP 15C and INT(1/√(1-x),0,1)

[Dieter]

(01-08-2018 04:07 PM)salvomic Wrote:  I could try a confrontation between a classic and a Limited edition HP15.
They started in the same instant, running to calculate the “not trivial” integral: ∫(1/(√(1-x)),0,1) that’s close 2.

The indefinite integral is –2√(1–x) so the integral from 0 to 1 is exactly 2.

(01-08-2018 04:07 PM)salvomic Wrote:  After 50 mins the classic 15C (FIX 4) was still running, instead the LE (FIX 6) gave up with “Error 0” message ("Improper mathematics operation": why?)

You can find out yourself: as soon as the error occurs, switch to program mode an see at which line you are. Since the stack is filled with x, press R↓ to check x.

I suspect that the error is caused by the 1/x instruction, and this may happen if x is so close to 1 that 1–x is evaluated to zero, which leads to an attempt to divide by zero. But this is just a guess. ;-)

This usually does not happen as the interval should not be evaluated at its limits. But if Δx eventually becomes extremely small this may well be possible.

Dieter