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We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) andSuzaku observations of the X-ray binary Cygnus X-1 in the hard state. This isthe first time this state has been observed in Cyg X-1 with NuSTAR, whichenables us to study the reflection and broad-band spectra in unprecedenteddetail. We confirm that the iron line cannot be fit with a combination ofnarrow lines and absorption features, and instead requires a relativisticallyblurred profile in combination with a narrow line and absorption from thecompanion wind. We use the reflection models of Garcia et al. (2014) tosimultaneously measure the black hole spin, disk inner radius, and coronalheight in a self-consistent manner. Detailed fits to the iron line profileindicate a high level of relativistic blurring, indicative of reflection fromthe inner accretion disk. We find a high spin, a small inner disk radius, and alow source height, and rule out truncation to greater than three gravitationalradii at the 3{\sigma} confidence level. In addition, we find that the lineprofile has not changed greatly in the switch from soft to hard states, andthat the differences are consistent with changes in the underlying reflectionspectrum rather than the relativistic blurring. We find that the blurringparameters are consistent when fitting either just the iron line or the entirebroad-band spectrum, which is well modelled with a Comptonized continuum plusreflection model.

NuSTAR and Suzaku observations of the hard state in Cygnus X-1: locating the inner accretion disk