[填空题]
Two Polaroids are aligyo a : *mvij:yf8y2x:gn-+2x aewoamw1 z. i9 o1* wuu9sgcmq.eed so that the light passing through them is a maximum. At what angle should one of them be placed so that the intenc*o+e1-ew. wixzu29m w. 1u ogm9aqassity is subsequently reduced by half? $^{\circ}\,$
