HP 12C "Solve LOG from TVM funtions" - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: General Forum (/forum-4.html) +--- Thread: HP 12C "Solve LOG from TVM funtions" (/thread-9316.html) HP 12C "Solve LOG from TVM funtions" - Gamo - 10-17-2017 08:31 AM LOGARITHMS FOR ANY BASE The following keystrokes solve for the exponent c in the equation A^c = B when A and B are known. This procedure may be labeled "finding the logarithm of B to the base A". The natural logarithm of B will again be available in the y register Keystrokes: 1. A ENTER 1 - 100 x [i] -1 [PV] B [FV] [N] --------> c 2. [X<>Y] ---------------------------------------------> ln B (base e) "this only work on HP-80" Example: Find the exponent c in the equation: 16^c = 4096 1. 16 ENTER 1 - 100 x [i] -1 [PV] 4096 [FV] [N] -> answer 3.00 (log 4096, base 16) 2. [X<>Y] -------------------------------------------> answer 8.32 (ln 4096, base e) RE: HP 12C "Solve LOG from TVM funtions" - Joe Horn - 10-17-2017 12:10 PM Wouldn't this be simpler? B [LN] A [LN] [÷] Example: Find the exponent c in the equation: 16^c = 4096 4096 [LN] 16 [LN] [÷] -> answer 3.00 (log 4096, base 16) RE: HP 12C "Solve LOG from TVM funtions" - Gamo - 10-17-2017 02:43 PM Thank You Joe I just wanna show that this can be done with TVM functions. Your procedures is much simpler too. Gamo RE: HP 12C "Solve LOG from TVM funtions" - bshoring - 10-22-2017 09:21 PM Joe's right. However, because the first two HP Financial calculators do not have the LN function, HP did provide a way to compute LOG & LN using the financial keys on the HP-80, and LOG on the HP-70. Since the HP-80 does all its computations in the stack, if you follow HP's instructions to get a LOG, the LN is automatically left in the Y register. HP-70, like all that follow, uses dedicated financial registers, so the Y reg will not contain LN, but there still is a way to compete LN on it if one puts the right input into the Interest (i) register.