The points AAA, BBB, C C\,C and D D\,D have position vectors a=i−2j+3k\mathbf{a} = \mathbf{i} - 2\mathbf{j} + 3\mathbf{k}a=i−2j+3k, b=5i+4j−k\mathbf{b} = 5\mathbf{i} + 4\mathbf{j} - \mathbf{k}b=5i+4j−k, c=−3i+2j+k\mathbf{c} = -3\mathbf{i} + 2\mathbf{j} + \mathbf{k}c=−3i+2j+k and d=3i+11j−5k\mathbf{d} = 3\mathbf{i} + 11\mathbf{j} - 5\mathbf{k}d=3i+11j−5k
Show that AB⃗\vec{AB}AB is parallel to CD⃗\vec{CD}CD
