d = \frac{90}{[α_{1}] - [α_{2}]} = \frac{90}{41, 5 - 31, 1} = 8, 65 m m

${d=\frac{90}{[\alpha_1 ]-[\alpha_2 ]}=\frac{90}{41,5-31,1}=8,65\, \mathrm{mm}}$

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