α∩β=L,EA⊥α,垂足为A,EB⊥β,垂足为B,a在β内,a⊥AB.求证:a//L

问题描述:

α∩β=L,EA⊥α,垂足为A,EB⊥β,垂足为B,a在β内,a⊥AB.求证:a//L