FIR filter coefficients using matlab command

I have a triangular window based two-cycle lowpass filter with coefficients given by , where , and N is the order of the filter. The order is dependent on the sampling frequency employed by the system. I have 2 questions regarding the same:

1) What if i want to determine the cut-off frequency of the same filter using these coefficients, since i only have the coefficients with me and nothing else?

2) If the first part is done how do i design a filter with the same time domain coefficients using "fir1" command?