If →a,→b,→c are non-coplanar vectors and →d is a unit vector then find the value of ∣∣(→a.→b)(→b×→c)+(→b.→d)(→c×→a)+(→c.→d)(→a×→b)∣∣ independent of →d
A
[→a,→b,→c]
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
[→b,→c,→a]
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
[→a−b,→b,→c]
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
[→a−b,→b−c,→c−a]
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is A[→a,→b,→c] ∣∣∣(→a.→b)(→b×→c)+(→b.→d)(→c×→a)+(→c.→d)(→a×→b)∣∣∣=∣∣∣(→a.→b)(→b×→c)−(→c.→d)(→b×→a)+(→b.→d)(→c×→a)∣∣∣=∣∣∣→b×[(→a.→b)→c−(→c.→d)→a]+(→b.→d)(→c×→a)∣∣∣=∣∣∣→b×{(→a×→c)×→d}+(→b⋅→d)(→c×→a))∣∣∣=∣∣∣(→b.→d)(→a×→c)−{→b.(→a×→c)}→d−(→b.→d)(→a×→c)∣∣∣=∣∣∣[→b→a→c]∣∣∣=[→b→a→c]∣∣∣→d∣∣∣∵∣∣∣→d∣∣∣=1=[→b→a→c]