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1. Let A be a symmetric matrix with eigenvalues λ₁, λ₂, ..., λₙ. It is known that there exists an orthogonal matrix C such that A = CDC⁻¹, where D = diag(λ₁, λ₂, ..., λₙ).
Use this fact to prove the following:
a) A = X * X⁻¹, where A is the determinant of A.
b) trace(A) = λ₁ + λ₂ + ... + λₙ.