  Quasi-periodic fast propagating (QFP) waves are often excited by solar
flares, and could be trapped in the coronal structure with low Alfv\'en speed,
so they could be used as a diagnosing tool for both the flaring core and
magnetic waveguide. As the periodicity of a QFP wave could originate from a
periodic source or be dispersively waveguided, it is a key parameter for
diagnosing the flaring core and waveguide. In this paper, we study two QFP
waves excited by a GOES-class C1.3 solar flare occurring at active region NOAA
12734 on 8 March 2019. Two QFP waves were guided by two oppositely oriented
coronal funnel. The periods of two QFP waves were identical and were roughly
equal to the period of the oscillatory signal in the X-ray and 17 GHz radio
emission released by the flaring core. It is very likely that the two QFP waves
could be periodically excited by the flaring core. Many features of this QFP
wave event is consistent with the magnetic tuning fork model. We also
investigated the seismological application with QFP waves, and found that the
magnetic field inferred with magnetohydrodynamic seismology was consistent with
that obtained in magnetic extrapolation model. Our study suggest that the QFP
wave is a good tool for diagnosing both the flaring core and the magnetic
waveguide.
