Your first column of L1 is derived from something minus itself, so the first column is going to be all 0.
Your second column of L1 is derived from something minus itself, so the second column is going to be all 0.
Your third-column is generally non-zero.
Cross-product of [0; 0; something] and [0; 0; something_else] is always going to be 0
>> syms x1 x2 y1 y2
>> cross([x1;y1;z1],[x2;y2;z2])
ans =
y1*z2 - y2*z1
x2*z1 - x1*z2
x1*y2 - x2*y1
but your x1 and x2 and y1 and y2 are all 0, and every term involves one of those variables, so every term is going to come out 0. Therefore your cross-product will come out 0 .
Best Answer