Out[1]= {{0.605062, 0.78659, 0.705669}, {0.0363308, 0.416557,
0.259851}, {0.34089, 0.187001, 0.5774}}
In[2]:= matrix /. {matrix[[1, 1]] -> x, matrix[[2, 2]] -> y,
matrix[[3, 3]] -> z}
Out[2]= {{x, 0.78659, 0.705669}, {0.0363308, y, 0.259851}, {0.34089,
0.187001, z}}
In[1]:= y[x_] = x^2;
a = 0;
b = 3;
In[4]:= Integrate[(1 + y'[x]^2)^(1/2), {x, a, b}]
Out[4]= 1/4 (6 Sqrt[37] + ArcSinh[6])
