(→a.^i)(→a×^i)+(→a.^j)(→a×^j)+(→a.^k)(→a×^k) is always equal to
None of these
→a=a1^i+a2^j+a3^k⇒→a.^i=a1, →a.^j=a2, →a.^k=a3
→a×^i=(a1 ^i+a2 ^j+a3 ^k)×^i=−a2 ^k+a3 ^j
Similarly, →a×^j=a1 ^k−a3 ^i, →a×^k=−a1 ^j+a2 ^i⇒(→a.^i)(→a×^i)+(→a.^j)(→a×^j)+(→a.^k)(→a×^k)=−a1a2 ^k+a1a3 ^j+a1a2 ^k−a3a2 ^i−a3a1 ^j+a3a2 ^i=→0