Baker, Campbell, and Hausdorff (1897-1906)

Intelligent Set of individuals who worked out that for Matrix Exponential

eAeB=exp(A+B+12[A,B]+112[A,[A,B]]−112[B,[A,B]]+⋯ )e^A e^B = exp(A+B+\frac{1}{2}[A,B]+\frac{1}{12}[A,[A,B]]-\frac{1}{12}[B,[A,B]]+\cdots)

if [A,B]=0[A,B]=0, then it is trivial as eAeB=eA+Be^A e^B = e^{A+B}