Using the definitions of $$total$$ pressure $($p$\backslash$deg $)$ and $$total$$ temperature $($T$\backslash$deg $),$ along with isentropic

relations, show that:

$$s $=$ cp ln$($T$2/$T$1)$ R ln$($p $2/$p $1)=$ cp ln$($T$\backslash$deg $2/$T$\backslash$deg $1)$ R ln$($p$\backslash$deg $2/$p$\backslash$deg $1)$

b$)$ Use a very simple T$-$s diagram to explain why this equality holds