function inertia_ijk = partial_inertia_matrix( xi,yi, xj,yj, xk,yk, h, rho )
% •”•ªŠµ�«�s—ñ‚ðŒvŽZ
    S = (1/2)*det([xj-xi, xk-xi; yj-yi, yk-yi]);
    I = eye(2);
    inertia_ijk = (rho*h*S/12) * [2*I, I, I; I, 2*I, I; I, I, 2*I];
end
