FTP, identify these functions named for their discoverer, a German astronomer and mathematician.
Euler's study of the vibrations of a stretched membrane, and Daniel Bernoulli's studies of the oscillations of a chain suspended by one end led to earlier formulations of some of them.  When Laplace's equation is formulated in cylindrical coordinates, these functions arise in the solution.  Discovered by their namesake during a study of solutions of Kepler's equations, they are important in describing the deformation of elastic bodies, the diffraction of light, and the flow of heat or electricity through a solid cylinder.  FTP, identify these functions named for their discoverer, a German astronomer and mathematician.
Euler's study of the vibrations of a stretched membrane, and Daniel Bernoulli's studies of the oscillations of a chain suspended by one end led to earlier formulations of some of them.  
Bessel function (prompt on "cylinder function")