Solution
= Solution
With cyclic spatial indices,
$$
J_1=M^{23},\quad J_2=M^{31},\quad J_3=M^{12},
\qquad K_i=M^{0i}.
$$
Substitution in the given <Poincare algebra> brackets yields
$$
[J_1,J_2]=J_3,
\qquad [J_1,K_2]=K_3,
\qquad [K_1,K_2]=-J_3.
$$
= Solution
With cyclic spatial indices,
$$
J_1=M^{23},\quad J_2=M^{31},\quad J_3=M^{12},
\qquad K_i=M^{0i}.
$$
Substitution in the given <Poincare algebra> brackets yields
$$
[J_1,J_2]=J_3,
\qquad [J_1,K_2]=K_3,
\qquad [K_1,K_2]=-J_3.
$$