Evaluate

Since |AB|= |A||B|

= 2(17×12 – 5×20) – 3(13×12 – 5×15) + 7(13×20 – 15×17)

= 2(204 – 100) – 3(156 – 75) + 7(260 – 255)

= 2×104 – 3×81 + 7×5

= 208 – 243 +35

= 0

Now |A|² = |A|×|A|

|A|²= 0