Matrix Differential Calculus with Applications in Statistics and Econometrics, 3rd Edition
by Jan R. Magnus, Heinz Neudecker
Chapter 8Some important differentials
1 INTRODUCTION
Now that we know what differentials are and have adopted a convenient and simple notation for them our next step is to determine the differentials of some important functions. We shall discuss the differentials of some scalar functions of X (eigenvalue, determinant), a vector function of X (eigenvector), and some matrix functions of X (inverse, Moore‐Penrose (MP) inverse, adjoint matrix).
But first, we must list the basic rules.
2 FUNDAMENTAL RULES OF DIFFERENTIAL CALCULUS
The following rules are easily verified. If u and v are real‐valued differentiable functions and α is a real constant, then we have
and also
The differential of the power function is
where the domain of definition of the power function uα depends on the arithmetical nature of α. If α is a positive integer, then uα is defined for all real u; but ...
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