[填空题]
A 35-mm slide (picture size is aca wrob3 wyz18)tually 24 by 36 mm) is to be projecte s vku7r7mz1m:d on a screen 1.80 m by 2.70 m placed 7.50 m from the projector.m:77uvrs 1m kz What focal-length lens should be used if the image is to cover the screen? cm
