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JEE Main 2019
Matrices & Determinants
Matrices and Determinants
Medium

Question

If α\alpha + β\beta + γ\gamma = 2π\pi, then the system of equations x + (cos γ\gamma)y + (cos β\beta)z = 0 (cos γ\gamma)x + y + (cos α\alpha)z = 0 (cos β\beta)x + (cos α\alpha)y + z = 0 has :

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Solution

Key Concept: Nature of Solutions for Homogeneous Linear Systems

A system of linear equations is called homogeneous if all the constant terms are zero. Such a system can be written in matrix form as AX=0AX = 0, where AA is the coefficient matrix, XX is the column vector of variables, and 00 is the zero column vector.

For a homogeneous system AX=0AX = 0:

  1. If the determinant of the coefficient matrix, Δ=det(A)\Delta = \det(A), is non-zero (Δ0\Delta \neq 0), the system has only the trivial solution (x=0,y=0,z=0x=0, y=0, z=0). This is a unique solution.
  2. If the determinant of the coefficient matrix,

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