To eliminate p from above equation, we consider the momentum equation 中p=-pd pldr=p u+y 2 2 02,02 Since the flow we are considering is isentropic, so dp dpTo eliminate from above equation, we consider the momentum equation :  dp = −VdV ( ) 2 2 2 2 2 dp = − VdV = − dV = − d u + v            +   = − 2 2 ( ) ( ) 2 x y dp d    Since the flow we are considering is isentropic, so 2 a p d dp s =           =  