In[]:=
deploy
Thu 1 Aug 2019 00:26:30
In[]:=
ContourPlot[{x,y}.{{1,0},{0,2}}.{x,y},{x,-2,2},{y,-2,2},ContourShadingNone]
Out[]=
In[]:=
{x,y}.{{1,0},{0,2}}.{x,y}
Out[]=
2
x
+2
2
y
In[]:=
ContourPlot[{x,y}.RotationMatrix[Pi/4].{{1,0},{0,2}}.RotationMatrix[-Pi/4].{x,y},{x,-2,2},{y,-2,2},ContourShadingNone]
Out[]=
In[]:=
{x,y}.RotationMatrix[Pi/4].{{1,0},{0,2}}.RotationMatrix[-Pi/4].{x,y}//FullSimplify
Out[]=
1
2
(3
2
x
-2xy+3
2
y
)