<Table> <Tr> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> (a) </Td> <Td> (b) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> (a) </Td> <Td> (b) </Td> </Tr> <P> Fig. 1 . Mach number in transonic airflow around an airfoil; M <1 (a) and M> 1 (b). </P>

In air the speed of sound s in meters per second is a linear function