Задача 40837.

The converging lens with a focal length of 6 cm gives a divergent beam of light, the angle between the extreme rays of the beam 2a = 90 °. Find the distance from the point light source to the lens if its radius of 3 cm.

The solution formulas and the laws of recording used in the decision, drawing, calculation formula and the withdrawal response.
If you have any questions about the decision to write. I try to help.