# RegionPlot3D Error

I have the following command:

RegionPlot3D[
Log[p1/(1 + p2)] > 0, {p1, 0, 0.5}, {p2, 0.5, 1}, {C, 0, 1}]


and my Mathematica 9 gave me the following error message:

RegionPlot3D::boolf: "Log[p1/(1+p2)]>0 must be a Boolean function."

I have no idea why Log[p1/(1+p2)]>0 is not a Boolean function. It just looks like an innocent inequality that should work in RegionPlot3D.

Note: I have simplified the inequality so it does not involve C, but in the original version it does contain C.

• I think that's because your p1 begin with 0, where the Log[p1/(1 + p2)] is undefined. Try TrueQ[Log[p1/(1 + p2)] > -2]. Jun 19, 2013 at 6:41

I think that's because your p1 begin with 0, where the Log[p1/(1 + p2)] is undefined. You could set the start point a little greater than 0, or you could try TrueQ[Log[p1/(1 + p2)] > -2], which will give False for any case that it's argument is not explicit True.
btw. You should not use C, which is a system reserved function, as your variable name.
• Similarly, avoid K which does not have its own doc page, but shows up via ?K. Jun 19, 2013 at 14:14