# How to express Log[b,x] in traditional format in Epilog without changing to base e

I'm having difficulty understanding how to express text in Epilog that is dynamically updated using Log[b, x]. Mathematica changes this to base $e$, but I would like it to be Log[b, x] in traditional format with base $b$, and I can't seem to make it work. I'm guessing I need to break the $\log$ apart using boxes or something, but don't know how to make a subscript that is a dynamically updated b value. Any ideas?

Manipulate[
Plot[{b^x, x, Log[b, x]}, {x, -10, 10},
PlotRange -> {{-5, 5}, {-10, 10}}, PerformanceGoal -> "Quality",
ImageSize -> All,
Epilog -> {Text[b^x, {-3, 4}], Text[Log[b, x], {3, -5}]},
GridLines -> {Range[-10, 10, 1], Range[-10, 10, 1]},
GridLinesStyle -> Opacity[.04]], {{b, 2, "Choose a base"}, 0.01, 4}]

• Epilog -> {Text[Subscript[Log, b] "(x)", {3, -5}]}] – Dr. belisarius Jan 16 '16 at 6:48

The code in the OP will work right off the bat if the following (sadly undocumented) setting is first executed:

SetSystemOptions["SimplificationOptions" ->
{"AutosimplifyTwoArgumentLog" -> False}]


After running that line, the Manipulate[] works as expected: Here's a way that let's Mathematica take care of the typesetting. Use With to inject the value of b into a held expression for the logarithm (see HoldForm).

Epilog -> {Text[b^x, {-3, 4}], Text[With[{b = b}, HoldForm@Log[b, x]], {3, -5}]} Thanks to Dr. Belisarius,

Epilog -> {Text[Subscript[Log, b] "(x)", {3, -5}]}]

• I think this Text[Row[{Subscript[Log, b], "(x)"}], {3, -5}] is preferrable. – Mike Honeychurch Jan 16 '16 at 22:41