  The vacuum energy density of electromagnetic field inside a perfectly
conducting wedge is calculated by making use of the local zeta function
technique. This regularization completely eliminates divergent expressions in
the course of calculations and gives rise to a finite expression for the energy
density in question without any subtractions. Employment of the Hertz
potentials for constructing the general solution to the Maxwell equations
results in a considerable simplification of the calculations. Transition to the
global zeta function is carried out by introducing a cutoff nearby the cusp at
the origin. Proceeding from this the heat kernel coefficients are calculated
and the high temperature asymptotics of the Helmholtz free energy and of the
torque of the Casimir forces are found. The wedge singularity gives rise to a
specific high temperature behaviour $\sim T^2$ of the quantities under
consideration. The obtained results are directly applicable to the free energy
of a scalar massless field and electromagnetic field on the background of a
cosmic string.
