fourfour basic operationsfour color conjecturefour color problemfour color theoremfour facefour fundamental operationsfour groupfour leaf cloverfour petaledfour petaled rosefour principal operationsfour sidedfour square theoremfour step rulefour way valvefourfoldfourier analysisfourier coefficientsfourier cosine seriesfourier double integral theoremfourier integral theoremsfourier laplace transformfourier seriesfourier sine seriesfourier single integral theoremfourier stieltjes transformfourier theoremfourier transformfourthfourth degreefourth degree polynomialfourth proportionalfourth quadrantfractilefractionfraction defectivesfraction in lowest termsfraction linefraction numberfractionalfractional cutfractional distillationfractional equationfractional exponentfractional idealfractional linearfractional linear transformationfractional partfractional power