Getting error when trying to use fabs

I have been getting the following error

 RooFormula::eval(fabs(Muon1_eta)<1.05&&fabs(Muon2_eta)<1.05): Formula doesn't compile: fabs(Muon1_eta)<1.05&&fabs(Muon2_eta)<1.05

My code resulting in this error is as follows:

 RooDataSet data("data", "Jpsi data set", tree,RooArgSet(jpsi, eta1, eta2), "fabs(Muon1_eta)<1.05&&fabs(Muon2_eta)<1.05");

I suspect it’s because I’m trying to use #include wrong. So far I’ve tried #include “math.h”, #include “<math.h>” and #include <math.h>. So far none of these are working and I’m left wondering what I’ve done wrong. Any help would be appreciated
ROOT Version: 6.14
Platform: Windows 10
Compiler: mobatek

Try TMath::Abs. The RooFormula doesn’t support all kinds of C++ expressions, but it should support the stuff in TMath: