Equazione 5.20 - Anderson Text

{\left( \frac{A_e}{A_t} \right )}^2 = \frac{1}{M^2} {\left[ \left(\frac{2}{\gamma + 1} \right ) \left( 1 + \left(\gamma - 1 \right ) \frac{M^2}{2}\right ) \right ]}^{\frac{\gamma + 1}{\gamma - 1}}