1) If a, b and c are unit vectors such that a+b+c=0 and (a,b)=π3, then |a×b|+|b×c|+|c×a|= A) 32 B) 0 C) 3√32 D) 3 Answer: Option CExplanation: We have, a,b,c are unit vector ∴ |a|=|b|=|c|=1 and a+b+c=0 , angle between a and b is π3 Now, a+b+c=0 ⇒ a×(a+b+c)=0 ⇒ a×a+a×b+a×c=0 ⇒ a×b=c×a ⇒ |a×b|=|c×a| Similarly , |a×b|=|c×a| ∴ |a×b|+|b×c|+|c×a| =3|a×b| =3|a||b|sin(a,b) =3×1×1×sinπ3=3√32