Розрахунок: dzn280 - 1

1

/ d

+

1

/ f

=

2

/ R

1

/ d

+

1

/ f

=

2

/ R

$\frac{1}{d}+\frac{1}{f}$ = $\frac{2}{R}$

1

/ d

=

2

/ R

-

1

/ f

$\frac{1}{d}$ = $\frac{2}{R}-\frac{1}{f}$

d =

1

/ (

2

/ R

-

1

/ f

)

$d$ = $\frac{1}{\frac{2}{R}-\frac{1}{f}}$