Cauchy–Riemann Characterisation of Complex Differentiability Complex Analysis LDL^T Factorisation of Positive-Definite Matrices Numerical Analysis Dual of a Quotient Space Analysis Banach-Steinhaus Theorem for Fréchet Spaces Functional Analysis Kuratowski Closure Axioms Topology $L^p$ Boundedness of the Hilbert Transform Analysis Dunford-Pettis Theorem Analysis Symbol Characterisation of Uniform Ellipticity Analysis Analysis Area