as known to all, we can find a matrix representation for every operator in quantum mechanics. for example for total angular momentum of one particle j(square) the elements are j(j+1)(square)h(bar) δmm' However I have stucked in two particle systems. for example I could not find the matrix of j1+j2- (this is a product) here j1+ is the raising operator for first particle and j2- is the lowering operator for second one. normally for one particle raising angular momentum operator gives the eigen value (squareroot)[j(j+1)-m(m+1)]. but in this case as far as i know, i have to find the matrix representration of product of this two operator. but for the below conditions I could not create a matrix. lets say j1=2 j2=1 and the restriction is m= m1 +m2 = 2. that is m1 can take values 2,1 and coresponding m2 values are 0 and 1. can you help me about this?