Confusions in windows based design of FIR filters?

I am reading the proakis book"DSP USING MATLAB 3rd Edition"

In chap 7, article 7.3, i came across example 7.8,where i saw formulas for pass band ripple and stop band attenuation I have highlighted them in attached snapshot but i couldn't find out how they were calculated

Please also include reference of these formulas of Rp and As, into your answer, as i could not find their reference in book

and also what is "delta_w"?Is it "transition width"?

• @engr: There are no "formulas", just think about what they're trying to do: they look at the magnitude response in dB and check its minimum value in the passband (where it should ideally be 0 dB), and its maximum value in the stopband (where it should ideally be 0, i.e., $-\infty$ dB). These are the maximum deviations from the ideal values, that's all. May 15 at 11:29