This textbook 'Applied Mathematics in Ferroelectricity and Piezoelectricity' was authored to provide the reader solid mathematical background for studying 'ferroelectricity and piezoelectricity', as a supplemental reference to my three course books; 'Ferroelectric Devices 2nd Edition (2010)', 'Micromechatronics 2nd Edition (2019)', and 'FEM and Micromechatronics with ATILA Software (2008)', all published from CRC Press. 'Physics' prefers 'simplicity'; converting a complicated phenomenon expressed by a function.