Scalar function is a function defined at each point in a certain domain in space. Its value is real and depends only on the point in space but not on any particular coordinate system being used.

A differential equation is an equation involving differentials or differential coefficients.

A transformation is a mathematical device which converts one function into another.

A complex number is an ordered pair of real numbers

A set S of points in the argand plane is said to be connected set if two of its points can be joined by a continuous curve, all of whose points belong to S.

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