hp prime

[joe1979]

Is there any way of changing the base number in logarithms

the LOG button is set to LOG10. how would i change the base so that i could have the log to base 3?

[Joe_Horn]

The easiest way to find the log of X base Y is LOG(X,Y).  Example: LOG(81,3) returns 4, because the log of 81 (base 3) is 4.  In Home, this is the easiest way because LOG and comma are primary keys.

Hint: in Home, press the Help key, then tap the Keys button, then press the LOG key.  Cool, huh?

You can also use the logb command, which looks nicer in Textbook Display mode.  It's the second-to-last item on the template key (next to the Toolbox key).

Caution: In CAS, LOG(x,y) must be spelled in uppercase, and logb(x,y) must be spelled in lowercase.  In Home, it doesn't matter.

Hope that helps!

[jsat]

Search the user manual for "logb" and "User Keyboard" for the answers, or just enter and run the following program:

   Export UserKey()    //an arbitrarily chosen program name

   BEGIN

   END;

   KEY K_Log()              //specifies the "LOG" key for modification of functionality

   BEGIN

   RETURN"logb(,3)";     //specified what you want returned when the "LOG" key is pressed

   END    

After running this code, press "Shift, User" prior to pressing LOG to execute the required base 3 log. Or press "Shift, User, Shift, User" to keep keep the user functionality active until you press "Shift, User" once more.

[solarfly]

I discovered the way to do this in RPN is 1 of two ways:

1: Log Template

a) Press the Math Template key and choose the logbN template (bottom row in the middle)

b) Fill in the base and argument and press Enter

c) Press Shift-,  (Eval)

  Example: [Template]  [LogbN]  [2]  >  [8] [Enter] [Shift] [,]

  The answer should be 3.

2: Quotes

a) Press Shift-( )  (quotes)

b) Press LOG

c) Enter the argument and base and press Enter

d) Press Shift-, (Eval)

  Example: [Shift]  ( )  [LOG] [8] [,] [2] [Enter] [Shift] [,]

Almost the same number of steps.