Calculator test

[C.Ret]

(12-06-2024 10:27 PM)Commie Wrote:  Key in \(ln(^-1)\) into your best calculator and hit return, your calculator should give \(\pi\cdot i\)

Hi Commie, your best calculators have a RETURN key ?

(12-07-2024 03:33 AM)Thomas Klemm Wrote:  

(12-06-2024 11:19 PM)Steve Simpkin Wrote:  I thought it would provide a complex answer like the HP-42S.

Complex results for real-number operations can be disabled with REALRES. This function sets flag 74.
Example
-1 LN
Invalid Data
But it still works for a complex number:
-1 i0 LN
0 i3.14159265359
It can be enabled with CPXRES. This function clears flag 74 (default).

This observation exactly match how the HP-15C works, except there is no specific command apart setting Flg 8 which is the complex-mode toggle or indicator.

(12-07-2024 01:22 PM)AnnoyedOne Wrote:  I activated complex mode (g SF 8), entered -1, then g Ln and got
0.0000
f Re<>Im gave 3.1416
which I believe is \(0+\pi\cdot i=\pi\cdot i/)

Right.
There is an alternative way of promoting complex mode on the HP-15C; it is simply to enter arguments as complex number.
So the same observation can be made, from 'standard' calculator state (the state we get after a reset [ON]+[ - ] ).

In 'real entry mode', results are strictly real:
[ 1 ][CHS][g][ LN ] display Error  0.
In 'extended complex stack mode', using one of the many entry methods:
[ 1 ][CHS][ENTER][ 0 ][f][ I ][g][ LN ] set the flag 8 and display real part 0.0000 and [f][(i)] or [f][Re⇋Im] display imaginary part 3.1416.

Unfortunately, there is no other way to quit the complex extend mode than clearing flag 8 by [f][ CF ][ 8 ] or by resetting the calculator.

Note, that trying the equation \(e^{\pi\cdot i}=^-1\) the opposite direction, show an interesting fact (or flow) about HP-15C precision in complex computations:
[g][ ∏ ][f][Re⇋Im][ ◀- ][ e^x ] exactly display real part -1.0000 but the imaginary part is not exactly what we expect; [f][(i)] or [f][Re⇋Im] display 4.1000  -10.

(12-07-2024 08:23 PM)Commie Wrote:  I've checked my hp15ce and yes it works, I'm growing to like my 15ce!

Really Commie? Even is there is no RETURN key on our beloved device?