If and , verify that |AB| = |A| |B|.
Now |A|= 2 × 1 – 2 × 5
|A|= 2 – 10
|A|= –8
Now |B|= 4 × 5 – 2 × (–3)
|B|= 20 + 6
|B|= 26
⇒ |A|×|B|= –8 × 26
|A|×|B|= –208
Now
|AB| = 18 × (–1) – 19 × 10
|AB| = –18 – 190
|AB| = –208
Hence |AB| =|A|×|B|.