The Principal Eigenvalue and The Principal Eigenfunction of A Boundary-Value-Transmission Problem

 It is well-know that the Sturm-Liouville theory justifies the "separation of variables"n method for voluminous partial differential equation problems. For Sturm-Liouville problems the Rayleigh quotient is  the basis of an important approximation method that is used in physics, as well as in engineering. Although any eigenvalue can be related to its eigenfunction by the Rayleigh quotient, this quotient cannot be used to determine the exact value of the eigenvalue since eigenfunction is unknown. However, interesting and significant results can be obtained from

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