The points AAA, BBB, C C\,C and D D\,D have position vectors a=2i−j+4k\mathbf{a} = 2\mathbf{i} - \mathbf{j} + 4\mathbf{k}a=2i−j+4k, b=5i+2j+k\mathbf{b} = 5\mathbf{i} + 2\mathbf{j} + \mathbf{k}b=5i+2j+k, c=−i+4j+6k\mathbf{c} = -\mathbf{i} + 4\mathbf{j} + 6\mathbf{k}c=−i+4j+6k, d=3i+8j+2k\mathbf{d} = 3\mathbf{i} + 8\mathbf{j} + 2\mathbf{k}d=3i+8j+2k
Show that AB⃗\vec{AB}AB is parallel to CD⃗\vec{CD}CD
