When the 'fatal error: helper_math.h: No such file or directory' occurs, it means the 'helper_math.h' file is missing.
In fact, 'helper_math.h' locates at '/usr/local/cuda/samples/common/inc/helper_math.h' if you've installed cuda successfully, so just copy the missing file to where the error occurs.
cp /usr/local/cuda/samples/common/inc/helper_math.h [Where the error occurs]