Write the values of  a1,..,a4,  b1,..,b4,  c1,..,c4,  d1,..,d4  in the boxes.  Then press the button.

a1 a2 a3 a4
b1 b2 b3 b4
c1 c2 c3 c4
d1 d2 d3 d4

                      determ. =
If you have to put a coefficient using some function symbol (for example 1/5, √2), put it in a numerical form (0.2, 1.414213562373095), for example using this (or this)