Let →V=2^i+^j−^k and −→W=^i+3^k. If →U is a unit vector, then the maximum value of the scalar triple product [→U →V −→W] is
→V×−→W=∣∣
∣
∣∣^i^j^k21−1103∣∣
∣
∣∣=3i−7^j−^k
⇒[→U →V −→W]=→U⋅(3^i−7^j−^k)=|U||3^i−7^j−^k|cosθ ⇒√59cosθ≤√59
The maximum value √59 is attained when θ=0∘