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Positive Definite Matrices

Definition

A matrix \(A\) is positive definite if:

  1. \(A\) is symmetric (\(A = A^T\))
  2. For all non-zero vectors \(x\), the quadratic form \(x^TAx > 0\)

You can verify if a matrix is positive definite if its corresponding eigenvalues are positive.

Example

References

Second Derivative Test