Printing determinant of a matrix

1

I am having trouble printing the determinant of a 5*5 square matrix. For simplicity, let’s consider the following code:

g_int = as_matrix([[1.2,0.0],[0.0,1.2]]) 
J_g_i = det(g_int)
print(J_g_i)

Now the print result is not giving me the value 1.2^2. Instead, it displays this:

det([
  [1.2, 0],
  [0, 1.2]
])

How do I get it to print the value of the determinant?