To compute the temperature distribution and heat fluxes in a square plate whose one side is kept at constant temperature T1 (boundary condition of the first kind), while the temperature of the air surrounding the remaining sides equals to Ta (boundary conditions of the second kind). We assume the third dimension to be unimportant (and especially \u2014 that there is no heat exchange). The coefficients of thermal conduction \xe1(alpha) and of heat exchange with surrounding air \xeb(lamda) are known.