why m=1, and why n=pi/2, 3pi/2, ………… The problem of unsteady heat conduction in a metal…

why m=1, and why n=pi/2, 3pi/2, …………

The problem of unsteady heat conduction in a metal plate of length 1 meter is described by the equation: where u is the temperature, with initial/boundary conditions: a(2,0) = 1 (0,t) = 1 Ou