1.
For positive numbers xx, yy and zz, the numerical value of the determinant
1logxylogxzlogyx1logyzlogzxlogzy1\begin{vmatrix} 1 & \log_x y & \log_x z \\ \log_y x & 1 & \log_y z \\ \log_z x & \log_z y & 1 \end{vmatrix}
is -