add subcaption package and single equation tag command

lecture.cls

@@ -26,9 +26,20 @@
 \RequirePackage{wasysym}
 \RequirePackage{environ}
 \RequirePackage{stackrel}
+\RequirePackage{subcaption}
 
 \usetikzlibrary{quotes, angles, math}
-\pgfplotsset{compat=1.15} % or \pgfplotsset{compat=newest}
+\pgfplotsset{
+    compat=1.15,
+    default 2d plot/.style={%
+        grid=both,
+        minor tick num=4,
+        grid style={line width=.1pt, draw=gray!10},
+        major grid style={line width=.2pt,draw=gray!50},
+        axis lines=middle,
+        enlargelimits={abs=0.2}
+    },
+}
 
 \geometry{
     bottom=35mm
@@ -250,3 +261,5 @@
 
 \ExplSyntaxOff
 
+% add one equation tag to the current line to otherwise unnumbered environment
+\newcommand{\tageq}{\stepcounter{equation}\tag{\theequation}}