v 4.4

E_{r 0} = \frac{n_{1} - n_{2}}{n_{1} + n_{2}} E_{i 0} E_{t 0} = \frac{2 n_{1}}{n_{1} + n_{2}} E_{i 0}

${E_{r0} = \frac{n_1 - n_2}{n_1 + n_2} E_{i0} \\ E_{t0} = \frac{2 n_1}{n_1 + n_2} E_{i0}}$

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