calling gaulegf(1.0, 2.0, x, w, n) 
x[1]=1.069432, w[1]=0.173927 
x[2]=1.330009, w[2]=0.326073 
x[3]=1.669991, w[3]=0.326073 
x[4]=1.930568, w[4]=0.173927 
area=2.333333