(a).

The intensity of light entering from a system of two polarizing lenses can be calculated by .

Where is the intensity of light entering the system of two polarizing lense.

is the angle of the axis of the second lense in relation to that of the first lense.

Consider .

Apply reciprocal identity : .

Apply Pythagorean identity : .

.

(b).

Consider .

Substitute in .

Therefore, of the intensity of the light entering the sunglasses emerges.

(a). .

(b). of the intensity of the light entering the sunglasses emerges.