hi all,
This may be more a general HP 42s question, but is there a way to use the LOG function with different bases?
LOG bases
Re: LOG bases
something like:
then
you could save a little program like this.
Otherwise, see here for a better solution, by Fernando: «The menu adds a the LGyX function to compute basey logarithm»...
Salvo
Code: Select all
input y (base)
ENTER
input x (number)
Code: Select all
LN
x<>y
LN
÷
Otherwise, see here for a better solution, by Fernando: «The menu adds a the LGyX function to compute basey logarithm»...
Salvo
∫aL√0mic (IT9CLU) :: DM42 (SN: 00881), DM41X (SN 00523), DM16, HP Prime, 50g, 41CX, 42s, 71b, 15C, 12C, 35s, WP34s  Free42
Re: LOG bases
Thank you. Interesting solution
I now use the solver and solve b^e=x for the exponent e, which works as well, but I just wondered if there was a trick to use LOG with a different base without resorting to solvers or programs. Apparently not.
Thanks for your reply though!
I now use the solver and solve b^e=x for the exponent e, which works as well, but I just wondered if there was a trick to use LOG with a different base without resorting to solvers or programs. Apparently not.
Thanks for your reply though!
Re: LOG bases
∫aL√0mic (IT9CLU) :: DM42 (SN: 00881), DM41X (SN 00523), DM16, HP Prime, 50g, 41CX, 42s, 71b, 15C, 12C, 35s, WP34s  Free42
Re: LOG bases
Do you mean this one:
LOGb(X) = LOG10(X)/LOG10(b)
If yes...no solver required
LOGb(X) = LOG10(X)/LOG10(b)
If yes...no solver required

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Re: LOG bases
That’s not a HP 42s trick, but a gaping gap in my fundamental knowledge and understanding of math in general and LOG / LN in particular!
I’m dedicating tonight to trying understand why LOGb(x) = LN(x)/LN(b), but indeed: no solver required!
Learning something new everyday, thank you guys!
I’m dedicating tonight to trying understand why LOGb(x) = LN(x)/LN(b), but indeed: no solver required!
Learning something new everyday, thank you guys!
Re: LOG bases
Just curious: why is it faster a LN than a LOG?
Re: LOG bases
Because LN is calculated while LG is derived from LN.
(Nitpicky remark: LG is identical to LOG10 like LN being identical to LOGe and LB to LOG2. Never let any mathematician catch you with a naked LOG in your text!)
DM42 SN: 00041 β
WP 43S running on this device
HP35, HP45, ..., HP35S, WP 34S, WP 31S, DM16L
WP 43S running on this device
HP35, HP45, ..., HP35S, WP 34S, WP 31S, DM16L