题目

Is there anybody out there? For centuries human beings have been wondering. As we've gained greater understanding of the universe, however, our searches have taken on a more concrete form. Questions about aliens have become a subject for science rather than science fiction and philosophy.Now a new cooperation(合作)between the Very Large Array observatory in New Mexico and the privately funded Seti Institute in California could mean that our curiosity about aliens is closer than ever before to being satisfied. Data from the VLA's 28 giant radio telescopes will be fed through a special superco如图，DE//AC，BE:EC=2:1，AC=12cm，则DE=_________cm