Ответ:

Объяснение:

№15

1/F=1/d+1/f

1/F=1/0.03м+1/0.18м=38.8м => F=1/38.8м≈0.026м

Г=|f/d|

Г=|0.18м/0.03м|=6

№16

α=90°-β

α=90°-50°=40°

№17

n=sinα/sinβ => sinα=nsinβ

sinα=4/3×0.3=0.4 => α=24°