| G = l (y1 − x2z + x3y) + m (y2 − x3x + x1z) + n (y3 − x1y + x2x). |
(8)
Differentiating with respect to t, and afterwards moving the fixed origin up to the moving origin O, so that
| x = y = z = 0, but | dx | = U, | dy | = V, | dz | = W, |
| dt | dt | dt |
| dG | = l ( | dy1 | − y2R + y3Q − x2W + x3V ) |
| dt | dt |
| + m ( | dy2 | − y3P + y1R − x3U + x1W ) |
| dt |
| + n ( | dy3 | − y1Q + y2P − x1V + x2U ) |
| dt |
= lL + mM + nN,
(9)
for all values of l, m, n.