In[]:=
Graphics[Circle[{0,0},1]]
Out[]=
In[]:=
ContourPlot[x^2+y^21,{x,-1,1},{y,-1,1}]
Out[]=
In[]:=
count=0
In[]:=
max=500
In[]:=
Do[​​x=RandomReal[{-1,1}];​​y=RandomReal[{-1,1}];​​If[x^2+y^2<1,{count=count+1}],max]
In[]:=
pie=4count/max
In[]:=
N[pie]