a · b = ax · bx + ay · by + az · bz = 2 · 4 + 4 · 6 + 6 · 2 =
= 8 + 24 + 12 = 44
b· c = bx · cx + by · cy + bz · cz = 4 · 2 + 6 · 4 + 2 · 2 =
= 8 + 24 + 4 = 36
