Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
MHT CET202617 April 2026Morning ShiftMathematicsVector AlgebraActual

Let a = (a₁ i + a₂ j + a₃ k ), b = (b₁ i + b₂ j + b₃ k ), c = (c₁ i + c₂ j + c₃ k ) be three non-zero vectors such that a is a unit vector perpendicular to both b and c . If the angle between b and c is 3 then vmatrix a₁ & a₂ & a₃ b₁ & b₂ & b₃ c₁ & c₂ & c₃ vmatrix ^2 =

Options

  1. A3 4 | b |^2| c |^2
  2. B1
  3. C0
  4. D1 4 | b |^2| c |^2

Correct answer

A. 3 4 | b |^2| c |^2

Step-by-step solution

The given determinant represents the scalar triple product of the vectors a , b , and c . vmatrix a₁ & a₂ & a₃ b₁ & b₂ & b₃ c₁ & c₂ & c₃ vmatrix = [ a b c ] = a ( b c ) Since a is perpendicular to both b and c , the vector a is collinear with b c . [ a b c ] = | a | | b c | Given that a is a unit vector, | a | = 1 . [ a b c ]^2 = | b c |^2 The angle between b and c is 3 . | b c |^2 = (| b | | c | ( 3 ) )^2 | b c |^2 = | b |^2 | c |^2 ( 3 2 )^2 = 3 4 | b |^2| c |^2 Answer: 3 4 | b |^2| c |^2

Practice Vector Algebra on Quantrex Academy →

More from Vector Algebra

P is the circumcentre of A B C . If the position vectors of A, B, C and P are a , b , c , a + b + c 4 respectively, then the position vector of the orthocentre of this triangle is 2025If the position vectors of A, B, C, D are i +2 j +2 k , 2 i - j , i + j +3 k and 4 j +5 k respectively, then the quadrilateral ABCD is a 2025The set of all real values of c so that the angle between the vectors a = cx i -6 j +3 k and b =x i +2 j +2 cx k is an obtuse angle for all real x is 2025Let a =2 i + j +3 k , b =3 i +3 j + k and c = i -2 j +3 k be three vectors. If r is a vector such that r a = r b and r c =18 , then the magnitude of the orthogonal projection of 4 2025If u , v , w are non coplanar vectors and p, q are real numbers, then the equality [ array lll 3 u & p v & p w array ]- [ array lll p v & w & q u array ]- [ array lll 2 w & q v & q 2025Let i -2 j + k , i + j -2 k , 2 i - j - k and i + j + k be the position vectors of four points A , B , C and D respectively. If a point P divides AB in the ratio 2: 1 internally an 2025If a = i + j , b =2 j - k are two vectors such that r a = b a , r b = a b , then the unit vector in the direction of r is 2025If a , b , c are three unit vectors such that a ( b c )= 3 2 b + c 2 and , are the angles between a , c and a , b respectively, then + = 2025 Full Vector Algebra list All MHT CET PYQs