diff --git a/Qk.h b/Qk.h
index 355b4ab..230e14b 100644
--- a/Qk.h
+++ b/Qk.h
@@ -2,6 +2,7 @@
 #define QK_H
 
 #include <cstdio>
+#include <cmath>
 
 double TauCal(double Energy_MeV){
 
diff --git a/ad++.h b/ad++.h
index 4df306f..0e57ab2 100644
--- a/ad++.h
+++ b/ad++.h
@@ -4,6 +4,8 @@
 #include "jSymbol.h"
 #include "Qk.h"
 
+#include <cmath>
+
 #include <TROOT.h>
 #include <TSystem.h>
 #include <TAxis.h>