function  J=jacobianRR(Q,L1,L2)

J=[-L1*sin(Q(1))-L2*sin(Q(1)+Q(2)) -L2*sin(Q(1)+Q(2))
    L1*cos(Q(1))+L2*cos(Q(1)+Q(2)) L2*cos(Q(1)+Q(2))];
end