Hermitian form of a spectral function in eigenbasis coordinates: $\operatorname{Re}(x^{\mathsf H} f(A) x) = \sum_i f(\lambda_i)\|c_i\|^2$

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Hermitian form of a spectral function in eigenbasis coordinates: $\operatorname{Re}(x^{\mathsf H} f(A) x) = \sum_i f(\lambda_i)\|c_i\|^2$ · Prove2Me